JP2000164214A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

[PROBLEMS] To provide a non-aqueous electrolyte secondary battery which can function sufficiently even at abnormal heat generation such as an internal short circuit or at a high temperature exceeding 60 ° C. and which is excellent in safety. . SOLUTION: The non-aqueous electrolyte secondary battery according to the present invention is a non-aqueous electrolyte secondary battery using a lithium-containing composite oxide that absorbs and releases lithium ions as a positive electrode active material. It is characterized in that the surface of the lithium oxide particles is coated with lithium spinel manganate or lithium spinel titanate.

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.

[0002]

2. Description of the Related Art With the rapid reduction in size and weight of electronic equipment, there is an increasing demand for the development of a secondary battery that is small, lightweight, has a high energy density, and can be repeatedly charged and discharged. . In addition, due to environmental problems such as air pollution and an increase in carbon dioxide, early commercialization of electric vehicles is desired, and development of excellent secondary batteries having characteristics such as high efficiency, high output, high energy density, and light weight. Is required.

As a secondary battery satisfying these requirements, a secondary battery using a non-aqueous electrolyte has been put to practical use. This battery has several times the energy density of a battery using a conventional aqueous electrolyte solution. For example, a cobalt composite oxide, nickel composite oxide or spinel lithium manganese oxide is used for the positive electrode of a non-aqueous electrolyte secondary battery, and a carbon material or tin oxide capable of inserting and extracting lithium is used for the negative electrode. Long-life 4V-class non-aqueous electrolyte secondary batteries have been put to practical use.

[0004]

In this non-aqueous electrolyte secondary battery, particularly in a battery using a lithium-cobalt-based composite oxide as a positive electrode active material, the charged state is 180 to 22.
Since the positive electrode active material is decomposed at around 0 ° C., the battery may be damaged during abnormal heat generation such as an internal short circuit. On the other hand, when used as a power source for a personal computer or the like, the temperature around the battery may exceed 60 ° C., and there is a demand for improvement in cycle performance at high temperatures. Therefore, it is an object of the present invention to provide a method for detecting abnormal heat generation such as an internal short circuit or the like.
It is an object of the present invention to provide a non-aqueous electrolyte secondary battery that can function sufficiently even at a high temperature exceeding 0 ° C. and is more excellent in safety.

[0005]

The non-aqueous electrolyte secondary battery according to the present invention is a non-aqueous electrolyte secondary battery using a lithium-containing composite oxide capable of inserting and extracting lithium ions as a positive electrode active material. The oxide is characterized in that the surface of lithium cobaltate particles is coated with lithium spinel manganate or lithium spinel titanate. In the lithium-containing composite oxide, the surface of primary particles of lithium cobaltate is coated with lithium spinel manganate or lithium spinel titanate, and the coating amount is 1 to 20% (mo
l). Further, the lithium-containing composite oxide is partially coated. In addition, it is characterized by combining these.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to a preferred embodiment, but it goes without saying that the present invention is not limited to the following without departing from the spirit of the present invention. FIG. 1 is an explanatory sectional view of a non-aqueous electrolyte secondary battery according to the present invention. In the figure, 1 is a non-aqueous electrolyte secondary battery, 2
Is an electrode group, 3 is a positive electrode plate, 4 is a negative electrode plate, 5 is a separator,
6 is a battery case, 7 is a case lid, 10 is a positive electrode terminal, 11
Is a positive electrode lead. The configuration of the nonaqueous electrolyte battery 1 is a prismatic lithium secondary battery in which a spiral electrode group 2 including a positive electrode plate 3, a negative electrode plate 4, and a separator 5 and an electrolytic solution are accommodated in a battery case 6. The battery case 6 has a thickness of 0.3 mm,
5mm thick on the surface of an iron body with outer dimensions 22 × 47 × 8.0mm
It has been subjected to nickel plating of μm, and an electrolyte injection hole (not shown) is provided on the upper side portion. In addition,
The positive electrode plate 3 is connected via a positive electrode lead 11 to a terminal 10 of a case lid 7 provided with a safety valve (not shown) and a positive electrode terminal 10. The negative electrode plate 4 is connected to the inner wall of the battery case 6 by contact. The battery is sealed by laser welding the lid 7 to the case 6. [Preparation of LiMn ₂ O ₄ coated LiCoO ₂ active material] 3% (mol) of LiCoO ₂
It hits the corresponding lithium acetate as the LiMn ₂ O ₄ (2.02
6g) and manganese acetate tetrahydrate (15.02 g) were dispersed in pure water. LiCoO ₂ (100 g) was added to the dispersion and dried. Next, the dried product was dispersed in methanol, dried and calcined to prepare a LiCoO ₂ active material in which LiMn ₂ O ₄ was coated at 3% (mol) with respect to LiCoO ₂ . At this time, the coating state of the coated LiCoO ₂ was such that LiMn ₂ O ₄ particles were scattered on the surface of the primary LiCoO ₂ particles. [Preparation of positive electrode plate] The current collector of the positive electrode plate had a thickness of 20 µm.
And an aluminum foil having a lithium-cobalt composite oxide as an active material. The positive electrode plate is composed of 8 parts by weight of polyvinylidene fluoride as a binder, 2 parts by weight of acetylene black as a conductive agent and LiMn ₂ O ₄ as LiCoO.
3% relative ₂ (mol) LiCoO ₂ active material 9 which is partially coated
And NMP (N-methyl-2-pyrrolidone), which is a solvent, as appropriate, to prepare a paste, which was then applied to both surfaces of the current collector material and dried. At this time, an uncoated portion was left in a rectangular shape as a lead portion. Then, it was manufactured by pressing to a thickness of 180 μm and cutting to a width of 19 mm. [Preparation of Negative Electrode Plate] The negative electrode plate was prepared by mixing 94 parts by weight of graphite as an active material and 6 parts by weight of polyvinylidene fluoride as a binder on both surfaces of a current collector made of a copper foil having a thickness of 14 μm, A paste prepared by appropriately adding NMP was applied to both sides and dried. At this time, an uncoated portion was left in a rectangular shape as a lead portion. And a thickness of 190
It was manufactured by rolling to μm and cutting to a width of 20 mm. [Separator] The separator has a thickness of 25 μm and a width of 22 m.
m is a microporous polyethylene membrane. The electrolyte is LiPF
A mixed solution of ethylene carbonate: diethyl carbonate = 1: 1 (volume ratio) containing 1 mol / l of ₆ was used. A battery (A) having the above-described structure according to the present invention and a conventional battery (B) were produced. However, in the conventional battery (B), as the positive electrode active material
The difference from the above configuration is that LiCoO ₂ is used. In addition, the active material according to the present invention is (a), and the conventional positive electrode active material is (b). The design capacity of the battery was 600 mAh. [Tests and Results] These batteries (A) and (B) were fully charged (charging conditions: 3 hours at a current of 1 C, constant-current / constant-voltage charging up to 4.1 V). After removing the positive electrode plate from (B), washing with dimethyl carbonate and drying in vacuum, the electrolyte solution (1 mol / l LiPF ₆ / EC
+ DEC (1: 1 by volume)) and DSC measurement (differential scanning calorimetry). The result is shown in FIG. From FIG.
In the conventional positive electrode plate (b) using uncoated LiCoO ₂ as an active material, heat generation is observed from around 220 ° C., and the DSC curve sharply rises. On the other hand, in the positive electrode active material using the active material according to the present invention, although heat generation is observed from around 200 ° C., the DSC curve does not rise sharply as in the conventional active material (b), and the peak is very gentle. Has formed. It was also shown that the exothermic peak shifted to 250 ° C. In addition, when the calorific value of both is calculated from the peak area, the calorific value of the positive electrode active material (a) according to the present invention is about 457 mJ / mg, and that of the conventional positive electrode active material (b) is about 692 mJ / mg. Was. From the above, it was clarified that the positive electrode active material (a) according to the present invention had better thermal stability than the conventional positive electrode active material (b). Next, using the batteries (A) and (B) according to the present invention, the capacity retention after 200 cycles at 25 ° C. and 60 ° C. was measured. The capacity retention was 2% of the initial discharge capacity.
The discharge capacity at the 00th cycle is shown as a percentage. Table 1 shows the results. (However, 3C at 1C current
Time, constant-current / constant-voltage charging was performed up to 4.1 V to reach a fully charged state, and discharging was performed at a current of 1 C to 2.75 V to make one cycle. )

[0007]

[Table 1]

According to Table 1, the battery (A) according to the present invention has a capacity of 2
More capacity than conventional battery (B) at both 5 ° C and 60 ° C
It was confirmed that the retention was good. Next,
10 batteries (A) and (B)
And using it at a current of 1 C for 3 hours, 4.1
V to constant current and constant voltage to reach full charge,
A nail piercing test was performed in which a battery having a diameter of 3 mm was pierced.
As a result, in the conventional battery (B), five out of ten cells were damaged.
On the other hand, in the battery (A) of the present invention,
No abnormalities were observed, indicating good safety.
Was. Note that, in the present embodiment, LiMn_TwoO_FourLiC quantity
oO_Two3% (mol), but 1% (mol) or less
Below, the effect of improving thermal stability was not recognized. Ma
Further, when the content is 20% (mol), the capacity decrease at a high temperature is large.
It's gone. Therefore, the coating amount is 1-20% (mol)
preferable. In addition, the coated state is
May be present, but preferably the electrolyte is LiCoO_TwoEnough contact
If possible, partially covered or porous coatings
A state with a large degree is preferred. In addition, spinel titanate
Spinel lithium manganate even when coated with titanium
Good safety can be obtained in the same manner as described above. However, a capacitive scale
Considering the degree, lithium spinel manganate is preferred
No. LiMn coating_TwoO _FourIn this embodiment,
Uses lithium acetate and manganese acetate tetrahydrate
But not limited to this, lithium and manga
Salts soluble in water or alcohols such as chloride
Substances, nitrates and the like. As chlorides and nitrates,
Lithium chloride, lithium nitrate, manganese chloride, man nitrate
A gun is exemplified. The battery according to the above embodiment has a rectangular shape.
However, shapes such as cylindrical, coin-shaped or paper-shaped
May be something. Also, regardless of the type of battery,
It goes without saying that it is applicable.

Further, the organic solvent is not fundamentally limited. The same effects as those of the present invention can be obtained as long as they are conventionally used for lithium batteries. For example, as a solvent, a low-viscosity solvent such as 1,2-dimethoxyethane, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl formate is mixed with a high dielectric constant solvent such as propylene carbonate, ethylene carbonate, γ-butyrolactone, and sulfolane. What was done can be used.

In the present invention, in the case of a non-aqueous electrolyte lithium ion secondary battery, the host material of the negative electrode may be any material as long as it can occlude and release lithium ions. For example, coke, carbon, amorphous carbon , SnO, SnO ₂ , Sn _1-x M _x O
(M = Hg, P, B, Si, Ge or Sb, provided that 0 ≦
_{X <1), Sn 1-} x M x O 2 (M = Hg, P, B, Si,
Ge or Sb, provided that 0 ≦ X <1), Sn ₃ O ₂ (OH)
₂ , Sn _3-x M _x O ₂ (OH) ₂ (M = Mg, P, B, S
i, Ge, Sb, As or Mn, provided that 0 ≦ X <3),
One or more selected from LiSiO ₂ , SiO _{2 and} LiSnO ₂ can be exemplified.

In the non-aqueous electrolyte secondary battery according to the present invention, the structure is a combination of a positive electrode, a negative electrode and a separator with a non-aqueous electrolyte, or an organic or inorganic solid electrolyte as the positive electrode, a negative electrode and a separator. Combination with water electrolyte, or positive electrode, negative electrode and separator,
A combination of an organic or inorganic solid electrolyte and a non-aqueous electrolyte,
Alternatively, a combination of an organic or inorganic solid electrolyte as a positive electrode, a negative electrode, and a separator with a non-aqueous electrolyte may be used. Of course, a non-aqueous electrolyte is unnecessary if it is an ion conductive solid electrolyte. Further, any known organic or inorganic solid electrolyte and non-aqueous electrolyte can be used as the separator or the separator.

[0012]

According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery which can function sufficiently even at the time of abnormal heat generation such as an internal short circuit or at a high temperature. Therefore, the industrial value of the present invention is extremely high.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of a non-aqueous electrolyte secondary battery according to an embodiment.

FIG. 2 is a diagram showing a DSC curve according to the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-aqueous electrolyte secondary liquid battery 2 Electrode group 3 Positive electrode plate 4 Negative electrode plate 5 Separator 6 Case 7 Lid 8 Safety valve 10 Positive electrode terminal 11 Positive electrode lead

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor So Lu 3-5-24 Miyahara, Yodogawa-ku, Osaka-shi, Honjo Chemical Co., Ltd. (72) Inventor Mikito Nagata Kichijoin Nishinosho, Minami-ku, Kyoto-shi, Kyoto Ino Babacho No. 1 In Japan Battery Co., Ltd. (72) Hiroyuki Yumoto Inventor No. 1 Nishinosho Inono Babacho, Kichijoin, Minami-ku, Kyoto, Kyoto Prefecture F-term in Japan Battery Co., Ltd. 5H003 AA10 BA02 BB05 BC01 BC05 BD03 5H029 AJ12 AK03 AL02 AL03 AL06 AL07 AL08 AM02 AM03 AM04 AM05 AM07 CJ21 CJ22 DJ12 DJ16 HJ02

Claims (3)

[Claims] 1. A non-aqueous electrolyte secondary battery using a lithium-containing composite oxide that absorbs and releases lithium ions as a positive electrode active material, wherein the lithium-containing composite oxide has a lithium cobaltate particle surface of lithium spinel manganate or A non-aqueous electrolyte secondary battery characterized by being coated with spinel lithium titanate. 2. The lithium-containing composite oxide, wherein primary particle surfaces of lithium cobaltate are coated with lithium spinel manganate or lithium spinel titanate,
The coating amount is 1 to 20% based on lithium cobalt oxide.
The non-aqueous electrolyte secondary battery according to claim 1, wherein 3. The method according to claim 1, wherein the lithium-containing composite oxide is partially coated.
The non-aqueous electrolyte secondary battery according to the above.