JP2963452B1 - Positive electrode active material and non-aqueous electrolyte secondary battery using the same - Google Patents

Abstract

The present invention provides a positive electrode active material having excellent cycle life characteristics in charge and discharge and a non-aqueous electrolyte secondary battery using the same. Non-aqueous electrolyte secondary battery used. Li _{1 + x} Mn _2-xyz A _y B _z O ₄ A = at least one element selected from Co, Ni, Fe, Cr B = at least one element selected from Mg, Zn, Ca 0 ≦ x ≦ 0. 09, 0.01 ≦ y ≦ 0.3, 0.01 ≦ z ≦
0.3

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improved positive electrode active material and a non-aqueous electrolyte secondary battery using the same.

[0002]

2. Description of the Related Art A nonaqueous electrolyte secondary battery uses, for example, lithium, a lithium compound, a lithium alloy or the like as a negative electrode, and uses propylene carbonate (PC), 1,2-dimethoxyethane (DME), γ-butyrolactone as an electrolyte. (Γ-BL),
Li in a non-aqueous solvent such as tetrahydrofuran (THF)
A non-aqueous electrolyte in which a lithium salt such as ClO ₄ , LiBF ₄ , LiAsF ₆ , or LiPF ₆ is dissolved is used, and transitions of TiS ₂ , MoS ₂ , V ₂ O ₅ , V ₆ O _13, etc. are mainly used as the positive electrode active material. Metal sulfide or oxide is used. On the other hand, MnO ₂ used for a nonaqueous electrolyte primary battery is considered to be used as a positive electrode active material of a secondary battery because of its low cost. Among them, LiMn ₂ O ₄ having a spinel structure is It is reported to have reversibility of charge and discharge.

[0003]

However, the above-mentioned secondary battery using LiMn ₂ O ₄ as a positive electrode active material has a problem in that the cycle life characteristics in charging and discharging are inferior.
In order to solve this, for example, Japanese Patent Laid-Open No.
(Li _1-y A _y ) x (Mn _1-z B _z ) ₂ O ₄ A = element selected from Na, K, Cu, Ag, Zn B = V, selected from Cr, Fe, Co, Ni Elements 0.9 ≤ x ≤ 1.1, 0.0 ≤ y ≤ 0.2, 0.0 ≤ z ≤ 0.
2, a divalent metal ion (for example, Mg, Ca, Zn, etc.) is added to LiMn ₂ O ₄ as disclosed in JP-A-3-108261.
A cathode active material to which Cd) has been added,

[0004] At least a portion of Mn of LiMn ₂ O ₄ crystal was replaced by Co in _{JP-A-4-160769, Li x Mn 2-y} M y O 4 M = Co, Ni, Fe, selected from Cr Positive electrode active materials represented by one kind of element: 0.85 ≦ x ≦ 1.15 and 0.3 <y ≦ 0.5 have been proposed, all of which have improved cycle life characteristics in charge and discharge. Still, it was not enough. An object of the present invention is to provide a positive electrode active material having excellent cycle life characteristics in charge and discharge, and a nonaqueous electrolyte secondary battery using the same.

[0005]

Means for Solving the Problems The present invention relates to a positive electrode active material represented by the following formula and a nonaqueous electrolyte secondary battery using the same. Li _{1 + x} Mn _2-xyz A _y B _z O ₄ A = at least one element selected from Co, Ni, Fe, Cr B = at least one element selected from Mg, Ca 0 ≦ x ≦ 0.09; 0.01 ≦ y ≦ 0.3, 0.01 ≦ z ≦ 0.3

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of a method for producing a positive electrode active material represented by the above formula of the present invention is shown below. For example, Li _{1 + x} Mn
The compound represented by the _{2-xyz Co y Mg z O} 4 is, Li compound,
It can be obtained by mixing the Mn compound, the Co compound, and the Mg compound so as to have a predetermined composition, and subjecting this mixture to heat treatment. Here, as the Li compound, for example, Li ₂ CO ₃ , L
IOH · H ₂ O, a LiNO ₃ or the like, as a Mn compound, for example MnO _2, the Mn ₃ O _4, MnCO _3, etc., as the Co compound, for example, _{Co 3 O 4, CoCO 3,} Co (OH) 2 , etc. And Mg compounds, for example, MgO, Mg (OH) _{2 and the} like. The heating temperature is usually in the range of about 650-1000 ° C., but the case of 750-900 ° C. is preferable because a better cycle life can be obtained.

Here, A is at least one element selected from Co, Ni, Fe, and Cr, and B is at least one element selected from Mg and Ca.
Co, B = Mg is preferred. Also, 0 ≦ x ≦ 0.09, 0.0
It is selected from the range of 1 ≦ y ≦ 0.3 and 0.01 ≦ z ≦ 0.3, of which 0 ≦ x ≦ 0.06 and 0.05 ≦ y ≦ 0.0.
3, preferably in the range of 0.05 ≦ z ≦ 0.3, particularly 0 ≦ x
≦ 0.03, 0.1 ≦ y ≦ 0.2, 0.1 ≦ z ≦ 0.2 are preferred.

In the present invention, a non-aqueous electrolyte secondary battery can be prepared using the above-mentioned positive electrode active material. In this non-aqueous electrolyte secondary battery, as the negative electrode and the electrolyte, those conventionally used conventionally can be used. For example, lithium, a lithium compound, a lithium alloy, carbon, or the like is used as a negative electrode, and ethylene carbonate (EC), diethylene carbonate (DEC), propylene carbonate (PC), 1,2-dimethoxyethane (DM) is used as an electrolyte.
E) LiClO ₄ , LiB in a non-aqueous solvent such as γ-butyrolactone (γ-BL), tetrahydrofuran (THF)
A non-aqueous electrolyte in which a lithium salt such as F ₄ , LiAsF ₆ , or LiPF ₆ is dissolved can be used.

The method for producing a non-aqueous electrolyte secondary battery can also employ the method conventionally used conventionally.
The nonaqueous electrolyte secondary battery obtained by using the above positive electrode active material of the present invention has excellent cycle life characteristics in charge and discharge, and the cycle life is apparent from the following Examples and Comparative Examples. About 6 times LiMn ₂ O ₄ , LiMn _1.7 Co
About 1.58 to 1.64 times the _{0.3 O 4, LiMn 1. 7 Mg} 0.3 O 4,
Furthermore, it has a remarkable effect of more than twice.

[0010]

The present invention will be described below with reference to examples and comparative examples. Examples 1 to 6 and Comparative Examples 1 to 7 Li ₂ CO ₃ , electrolysis—MnO ₂ , Co ₃ O ₄ , and MgO were weighed so as to have a predetermined composition, and then mixed in a mortar.
For 12 hours to synthesize the materials shown in Table 1. When the obtained material was subjected to powder X-ray diffraction, it was confirmed that the LiMn ₂ O ₄ phase was present as shown in FIGS.
In addition, 0.8 g of material, 0.13 g of acetylene black,
After kneading 0.07 g of polytetrafluoroethylene in a mortar and rolling to a thickness of 30 μm, Ni mesh (60 m
esh), dried under vacuum at 150 ° C. for 12 hours, and used for a battery cycle test. 1M LiC for electrolyte
lO ₄ + 50% ethylene carbonate (EC) + 50% diethylene carbonate (DEC) was used, and the counter electrode and the reference electrode were obtained by pressing a Li foil on Ni mesh (60 mesh). FIG. 3 shows a cell used in the battery test. The potential range was 3.3 to 4.3 V vs. Li / Li ⁺ , the current value was 49.4 mA per gram of the sample, and the temperature was 25 ° C.

Table 1 shows the charge / discharge cycle life. LiMn
It can be seen that a part of Mn in ₂ O ₄ is replaced by Co or Mg, and the cycle life becomes longer as the replacement amount increases. However, it can be understood that the simultaneous replacement of the two elements Co and Mg further increases the cycle life as compared with a material in which only one element of Co or Mg is replaced. further,
It can be seen that the cycle life is further extended by Li substitution with a material in which two elements of Co and Mg are substituted simultaneously. As described above, the cycle life can be further improved by simultaneously substituting a part of Mn in LiMn ₂ O ₄ with two elements of Co and Mg or three elements of Li, Co and Mg, rather than substituting one element by itself. It can be seen that is improved. The cycle life is the life when the discharge capacity is reduced to 80% of the discharge capacity in the first cycle, and is the number of cycles.

[0012]

[Table 1]

[0013]

According to the present invention, it is possible to provide a positive electrode active material having excellent cycle life characteristics in charge and discharge and a non-aqueous electrolyte secondary battery using the same.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of LiMn ₂ O ₄ and the positive electrode active materials obtained in Examples 1 to 3.

FIG. 2 is an X-ray diffraction diagram of LiMn ₂ O ₄ and the positive electrode active materials obtained in Examples 4 to 6.

FIG. 3 shows a cell used in a charge / discharge cycle test.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 4/58 H01M 10/40 H01M 4/00-4/02

Claims (2)

(57) [Claims] 1. A positive electrode active material represented by the following formula: Li _{1 + x} Mn _2-xyz A _y B _z O ₄ A = at least one element selected from Co, Ni, Fe, Cr B = at least one element selected from Mg, Ca 0 ≦ x ≦ 0.09; 0.01 ≦ y ≦ 0.3, 0.01 ≦ z ≦ 0.3 2. A non-aqueous electrolyte secondary battery using the positive electrode active material according to claim 1.