JPH05283077A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To prevent the elution of manganese included in the compound oxide into the nonaqueous electrolyte at the time of charge, and prevent the rise of the inner resistance to obtain the high efficient discharge characteristic by using a positive electrode, in which a specified compound oxide is used as active material. CONSTITUTION:This nonaqueous electrolyte secondary battery is provided with a negative electrode 2 mainly composed of lithium metal or the material, which can store and discharge lithium, and a positive electrode 1, in which a compound oxide expressed by a composition formula LiXMeyMnOZ (Me means at least one kind of element selected among the group of B, Si, P, Ga, Ge, As, Se, In, Sn, Sb, Te, Pb, Po and At; x, y and z means positive number) is used as active material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to improving the elution resistance of manganese contained in a manganese-containing positive electrode active material to a non-aqueous electrolyte.

[0002]

2. Description of the Related Art In recent years,
In a non-aqueous electrolyte secondary battery, Li ₂ MnO ₃ -containing MnO _{2 is} used as a positive electrode active material in order to increase the capacity.
₂ (see JP-A-63-114064), Li-containing MnO ₂ (see JP-A-1-235158), Li
Manganese-containing composite oxides such as Mn ₂ O ₄ (spinel) have been proposed.

Meanwhile, in the case of the non-aqueous electrolyte secondary cell of this type, in order to actually its high capacity, the positive electrode considerable high potential (usually against Li ⁺ / Li single electrode potential 3. It is necessary to charge until it reaches 6V or more).

However, when the positive electrode is charged to a high potential in this way, manganese in the manganese-containing composite oxide is eluted into the electrolyte to increase the internal resistance of the battery, which can withstand a large discharge current. That is, it becomes difficult to obtain a battery having excellent high rate discharge characteristics.

The present invention has been made to solve such a problem, and its purpose is to prevent manganese from being charged to a considerably high potential in order to increase the battery capacity. It is an object of the present invention to provide a non-aqueous electrolyte secondary battery which is excellent in high rate discharge characteristics with a small increase in internal resistance and which hardly elutes into the electrolyte.

[0006]

A non-aqueous electrolyte secondary battery according to the present invention (hereinafter, referred to as "invention battery") according to the present invention for achieving the above object can occlude and release lithium metal or lithium. Of a negative electrode containing as a main material a composition formula Li
_X Me _y MnO _Z (Me is B, Si, P, Ga, Ge,
At least one element selected from the group consisting of As, Se, In, Sn, Sb, Te, Pb, Po and At;
x, y and z are positive numbers) and a positive electrode using a composite oxide as an active material.

As the composite oxide represented by the composition formula Li _x Me _y MnO _Z , which is the positive electrode active material in the battery of the present invention,
Various values of the atomic ratio of Me: Mn, that is, y values in the composition formula can be used, but as shown in Examples described later, y values of 0.04 to 1.0 are used. It is preferable to use manganese because the elution of manganese into the electrolyte can be effectively suppressed and the increase in the internal resistance of the battery can be significantly suppressed. That is, when the value of y is less than 0.04, the effect of suppressing the elution of manganese due to the complexation of the Me compound and the manganese-containing composite oxide is not sufficiently exhibited because the amount of addition of Me is not sufficient. Even if the value exceeds 1.0, the effect of suppressing the elution of manganese according to the increase in the added amount of Me can hardly be expected, and the discharge capacity of the composite oxide as a positive electrode active material decreases, Both are not preferable.

The positive electrode using Li _X Me _y MnO _Z as the active material in the present invention is obtained, for example, as follows.
First, lithium hydroxide (LiOH), diboron trioxide (B ₂ O ₃ ), and manganese dioxide (MnO ₂ ) were mixed at a predetermined molar ratio and then at a temperature of 250 to 1000 ° C. for 20 minutes. Heat treatment for about an hour.

Then, if necessary, the active material thus obtained is pulverized to a predetermined particle size, and then acetylene black,
Conducting agents such as carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (P
VdF) and a binder, and the weight ratio is usually 80 to 90: 5.
It mixes at a ratio of about 15: 4 to 15 to obtain a positive electrode mixture.

Further, the positive electrode mixture is pressure-molded at a predetermined pressure (usually 0.5 to 1.5 ton / cm ² ), and the obtained molded product is made of stainless steel mesh as a current collector. It is rolled into a disk or the like and heat-treated (usually heated at about 100 to 250 ° C) to obtain a positive electrode.

The negative electrode in the battery of the present invention is mainly composed of lithium metal or a substance capable of inserting and extracting lithium. When lithium metal is used, it is processed into a predetermined size shape such as a disk shape by rolling, punching or the like, and is used.

As the substance capable of inserting and extracting lithium,
Examples include lithium alloys and carbon materials such as graphite and coke. When a powdery substance such as a carbon material is used, it is usually mixed with a binder and optionally a conductive agent in a weight ratio of about 80 to 90: 5 to 15: 4 to 10. After forming the negative electrode mixture, this negative electrode mixture is subjected to a predetermined pressure (usually,
0.5-1.5 ton / cm ² ) is pressure-molded, and the obtained molded product is rolled into a mesh disc as a current collector and heat-treated (usually at about 100 to 250 ° C.). It is heated) to make a negative electrode.

As described above, the battery of the present invention is a non-aqueous electrolyte secondary battery in which a lithium metal or a substance capable of inserting and extracting lithium is used as a main material of a negative electrode, and a specific composite oxide is used as a positive electrode active material. Has the greatest feature in that it is used, and therefore other members such as non-aqueous electrolytes, separators (when liquid electrolytes are used) are conventionally used for non-aqueous electrolyte secondary batteries. Alternatively, various proposed materials can be used.

[0014]

In the battery of the present invention, since the specific manganese-containing composite oxide is used as the positive electrode active material, even if the positive electrode is exposed to a high potential during charging for high capacity, the manganese-containing composite oxide is used. It is difficult for the manganese contained therein to be eluted into the electrolyte, and the internal resistance of the battery does not rise easily.

[0015]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to the following examples, and various modifications can be made without departing from the scope of the invention. Is possible.

Examples 1 to 4 [Preparation of Positive Electrode] Lithium hydroxide (LiOH), diboron trioxide (B ₂ O ₃ ) and manganese dioxide (MnO ₂ )
And Li: B: Mn atomic ratio is 0.58:
0.16: 1.00 (Example 1), 0.54: 0.0
8: 1.00 (Example 2), 0.52: 0.04: 1.
00 (Example 3), 0.51: 0.02: 1.00 (Example 4), and then heat treated at 850 ° C. for 20 hours to obtain four kinds of powdery positive electrode active materials. Got When each of these powdery positive electrode active materials was examined by an X-ray diffraction method, the presence of LiMn ₂ O ₄ and Li ₂ B ₄ O ₇ was confirmed.

Next, these positive electrode active materials were mixed with acetylene black as a conductive agent and fluororesin powder as a binder at a weight ratio of 90: 6: 4 to obtain four types of positive electrode mixture.

Further, 2 parts of each of these positive electrode mixtures are added.
It is pressure-molded at a pressure of ton / cm ^{2 into} a disk shape with a diameter of 20 mm, the obtained molded product is rolled into a stainless mesh disk as a current collector, and at 250 ° C for 2 hours under vacuum. It heat-processed and produced four types of positive electrodes.

[Production of Negative Electrode] A disk-shaped negative electrode made of lithium metal having a diameter of 20 mm was produced by rolling and punching.

[Preparation of Non-Aqueous Electrolyte Solution] A non-aqueous electrolyte solution was prepared by dissolving 1 mol / liter of lithium perchlorate in a mixed solvent of propylene carbonate and 1,2-dimethoxyethane at a volume ratio of 1: 1. ..

[Fabrication of Non-Aqueous Electrolyte Secondary Battery] A flat non-aqueous electrolyte secondary battery BA1 according to the present invention using the positive and negative electrodes, the non-aqueous electrolyte solution, a positive electrode can, a negative electrode can, etc.
(Example 1), BA2 (Example 2), BA3 (Example 3) and BA4 (Example 4) (all battery dimensions were diameter: 24 mm, thickness: 3 mm) were produced. As the separator, a microporous thin film made of polypropylene was used, which was impregnated with the above-mentioned non-aqueous electrolyte solution.

FIG. 1 is a sectional view of the manufactured battery BA1 (same for batteries BA2 to BA4).
Includes a positive electrode 1, a negative electrode 2, a separator 3, a positive electrode can 4, a negative electrode can 5, a positive electrode current collector 6, a negative electrode current collector 7, an insulating packing 8 made of polypropylene, and the like. Positive electrode 1 and negative electrode 2
Are housed in a battery case formed by positive and negative bipolar cans 4 and 5 facing each other with a separator 3 interposed therebetween. The positive electrode 1 is connected to the positive electrode can 4 via the positive electrode current collector 6, and the negative electrode 2 is connected to the negative electrode collector. It is connected to the negative electrode can 5 via the electric body 7 so that the chemical energy generated inside the battery BA1 can be taken out as electric energy from both terminals of the positive electrode can 4 and the negative electrode can 5.

(Comparative Example 1) In preparation of a positive electrode, lithium hydroxide (LiOH) was used without adding diboron trioxide.
Comparative battery BC1 was produced in the same manner as in Example 1 except that manganese dioxide (MnO ₂ ) was mixed so that the atomic ratio of Li: Mn was 0.5: 1.0.

Batteries BA1 to BA manufactured in Examples 1 to 4
4 and Comparative Battery BC1 manufactured in Comparative Example 1 were examined for the relationship between the charging time and the internal resistance of the battery when continuously charged at a constant charging voltage of 4.0V. The results are shown in Figure 2.

In FIG. 2, the vertical axis represents the internal resistance (Ω) of the battery,
Further, it is a graph in which charging time (weeks) is plotted on the horizontal axis, and ⊚ indicates battery BA1 (Mn: B = 1.0).
0: 0.16; y = 0.16), ○ indicates battery BA2 (M
n: B = 1.00: 0.08; y = 0.08), Δ indicates battery BA3 (Mn: B = 1.00: 0.04; y = 0.0)
4) and □ are batteries BA4 (Mn: B = 1.00: 0.0
2; y = 0.02), and x shows the results for the comparative battery BC1 (without boron compounding).

The batteries were used from the graph, the composite oxide Li _X B _y MnO _z containing boron BA1~BA4
It can be seen that in comparison with the comparative battery BC1 using the complex oxide containing no boron, the increase in internal resistance with the progress of charging is small. In particular, the battery BA1~BA3 using Li _X B _y MnO _z value of y is 0.04 or more as a positive electrode active material, it can be seen that the increase in internal resistance is remarkably restrained.

A comparative battery BC1 having an internal resistance higher than 20 Ω (internal resistance 48 Ω one week after starting charging) was disassembled and the negative electrode was examined by ICP analysis. It was found that Mn was precipitated. Similarly, the negative electrodes of the batteries BA1 to BA3 having an internal resistance of 18Ω or less after 12 weeks were also examined, but no precipitation of Mn was observed.

(Examples 5 to 56) Instead of boron (B), silicon (Si), phosphorus (P), gallium (Ga),
Germanium (Ge), arsenic (As), selenium (S)
e), indium (In), tin (Sn), antimony (Sb), tellurium (Te), lead (Pb), polonium (Po), or astatine (At) was used as an additive element. 52 as in Examples 1-4
Non-aqueous electrolyte batteries having different kinds of positive electrode active materials were prepared, and the internal resistance of each battery was measured 8 weeks after the start of charging. The atomic ratio of Li: Me (each additional element): Mn is 0.5 (y + 1): y: 1.
And

The results are shown in Table 1. In the table, the internal resistances of the batteries BA1 to BA4 produced in Examples 1 to 4 and the comparative battery BC1 produced in Comparative Example 1 at the time point 8 weeks after the start of charging are also shown. However, in the case of a battery having a resistance of more than 50 Ω before the elapse of 8 weeks, it is shown by x instead of the internal resistance value.

[0030]

[Table 1]

(Examples 57 to 112) The heat treatment temperature was set to 8
Non-aqueous electrolyte batteries of 56 kinds of positive electrode active materials different from each other were prepared in the same manner as in Examples 1 to 56 except that the temperature was changed to 375 ° C. instead of 50 ° C., and charging was started for each of these batteries. After 8 weeks, the internal resistance of the battery was measured. Note that Li: Me (each additional element): Mn
The atomic ratio was 0.5 (y + 1): y: 1.

The results are shown in Table 2. However, as in Table 1,
Batteries exceeding 50 Ω before 8 weeks had passed are indicated by x instead of the internal resistance value.

[0033]

[Table 2]

It can be seen from Tables 1 and 2 that the battery of the present invention has a smaller increase in the internal resistance at the time when 8 weeks have passed, as compared with the comparative battery BC1. Also, in particular, the value of y is 0.0
The 4 or more Li _X Me _y MnO _z in battery using as the positive electrode active material, it can be seen that the increase in internal resistance is remarkably restrained.

In the above embodiment, a specific example in which the present invention is applied to a flat type battery is described, but the shape of the battery is not particularly limited, and the present invention has various shapes such as a cylindrical shape and a square shape. It is applicable to non-aqueous electrolyte secondary batteries.

[0036]

EFFECT OF THE INVENTION In the battery of the present invention, since the positive electrode using the specific composite oxide as the active material is used, the elution of manganese contained in the composite oxide into the non-aqueous electrolyte during charging. It hardly happens, and the internal resistance hardly rises. Therefore, the present invention has excellent unique effects such as excellent high rate discharge characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a flat type non-aqueous electrolyte secondary battery according to the present invention.

FIG. 2 is a graph showing the relationship between the charging time and the internal resistance of the battery of the present invention and the comparative battery.

[Explanation of symbols]

 BA1 Flat type non-aqueous electrolyte secondary battery 1 Positive electrode 2 Negative electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Noma 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (72) Inventor Hiroshi Kurokawa 2-18 Keiyo Hondori, Moriguchi City, Osaka Sanyo (72) Inventor Mayumi Uehara 2-18 Keihan Hon-dori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (4)

[Claims] 1. A negative electrode containing lithium metal or a substance capable of occluding and releasing lithium as a main component, and a composition formula Li _X Me _y M.
nO _Z (Me is B, Si, P, Ga, Ge, As, S
e, In, Sn, Sb, Te, Pb, Po and at least one element selected from the group consisting of At; x, y and z are positive numbers) and a positive electrode using a composite oxide as an active material. A non-aqueous electrolyte secondary battery comprising: 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein _{y in the} composition formula Li _X Me _y MnO _Z is 0.04 or more and 1.0 or less. 3. M in the composition formula Li _X Me _y MnO _Z
The non-aqueous electrolyte secondary battery according to claim 1, wherein e is B and y is 0.04 or more and 1.0 or less. Wherein said composite oxide has a composition formula Li _X B _y MnO
Li ₂ B ₄ O ₇ represented by _Z (0.04 ≦ y ≦ 1.0)
The non-aqueous electrolyte secondary battery according to claim 1, which is a containing complex oxide.