JP2001250554A - Non aqueous electrolyte secondary cell having heat resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coin-shaped secondary cell of lithium ion, that resists reflow temperature and that generates a voltage, after constructing a cell. SOLUTION: For a positive electrode, LiMO2 (M is Co, Ni) is used and for a negative electrode, LiaCubTicO4 (0<a<=1, 0<b<=0.5, 1.5<c<=2), while metal lithium is connected to the negative electrode at constructing of a cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coin type secondary battery comprising lithium or a non-aqueous electrolyte having lithium ion conductivity and a heat-resistant gasket, wherein lithium or a substance capable of inserting and extracting lithium is used as a positive or negative electrode active material. .

[0002]

2. Description of the Related Art With the remarkable development of portable electronic devices and communication devices, a variety of devices that require a large current output from a battery as a power supply have appeared, and the viewpoint of economy and reduction in size and weight of the devices have been developed. Therefore, a high energy density secondary battery is strongly demanded. For this reason, research and development of non-aqueous electrolyte dual batteries having a high energy density have been actively conducted and put to practical use.

Conventionally, as a positive electrode active material of this type of secondary battery, molybdenum oxide, manganese oxide, and lithium-containing manganese oxide (LiMnO ₂ , Li ₄ Mn ₅
O ₁₂ ), lithium-containing cobalt oxide (LiCo
O ₂ ) and lithium-containing nickel oxide (LiNiO ₂ ). On the other hand, as the negative electrode active material, lithium metal or a lithium alloy absorbing and releasing lithium, activated carbon,
Silicon oxide, titanium oxide (TiO _2), lithium-containing titanium oxide _{(LiTi 2 O 4, Li 4} Ti 5 O 12), the composition formula _{Li a Cu b Ti c O 4} (0 <a ≦ 1,0 < b ≦ 0.
5, 1.5 ≦ c <2) and the like are used. A secondary battery made by combining these exhibits excellent characteristics with a large charge / discharge capacity. The negative electrode can be used as it is, or can be used after doping with lithium, depending on the positive electrode to be combined.If the negative electrode is used as it is, the battery voltage after assembly is 0 V. It has a battery voltage.

[0004]

However, a battery having a battery voltage after assembling by doping the negative electrode with lithium has a higher high-temperature storage characteristic than a battery having no battery voltage after assembling using the negative electrode as it is. There was a tendency to be inferior. This feature is particularly remarkable when the components of these batteries are assembled as heat-resistant members as coin-type heat-resistant batteries compatible with a reflow furnace and heat-treated in a reflow furnace. That is, a coin-type lithium ion secondary battery having a battery voltage after assembling by doping lithium into the negative electrode, by reflow heat treatment,
Increased battery internal resistance, battery swelling, liquid leakage, rupture, etc. are observed.However, in the case of coin-type lithium ion secondary batteries that use the negative electrode as it is and have no battery voltage after assembly, these characteristics are due to the reflow heat treatment of the battery. No deterioration is observed.

On the other hand, in order to confirm the electrical contact by soldering the battery and the battery characteristics after mounting this type of coin-type lithium ion secondary battery on the board, it is necessary to measure the battery voltage reliably and simply. This is a general confirmation method. For this reason, coin-type lithium-ion secondary batteries that use the negative electrode as it is and do not have a battery voltage after assembly are difficult to confirm after mounting on the board, despite the high reflow heat resistance, but it is difficult to adopt them at present. there were.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a coin-type secondary battery having a battery voltage after battery assembly and having high reflow heat resistance. Batteries having a battery voltage due to lithium doping of the negative electrode are inferior in high-temperature storage characteristics and reflow heat resistance because the chemical activity of the negative electrode active material is increased by lithium doping, and the active material itself is decomposed by heat and the solvent is oxidized. It is considered to cause a decomposition reaction.

Therefore, in the present invention, in a lithium ion conductive nonaqueous electrolyte, a substance reduced by lithium or a substance doped with lithium, and the reduced substance or the substance doped with lithium is thermally stable. A metal oxide to be a substance (hereinafter, referred to as a second component of the negative electrode active material) was present in the negative electrode.
Further, when assembling the battery, metallic lithium was electrically connected to the negative electrode.

Thus, after the battery is assembled, the potential of the negative electrode is reduced by reducing the second component of the negative electrode active material with metallic lithium or by doping lithium into the second component of the negative electrode active material, thereby reducing the battery voltage. A battery having the same. In addition, the present battery has reflow resistance and heat resistance because the substance reduced by lithium or the substance doped with lithium after the battery is assembled is thermally stable. That is, according to the present invention, a battery that is stable to reflow heat treatment and has a battery voltage after assembly can be produced.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As a positive electrode active material, an active material that contains mobile lithium and is thermally stable in the presence of a lithium ion conductive nonaqueous electrolyte and an active material can be used. As a cathode material, LiMO which is an oxide is used.
₂ (M is Ni and / or Co), LiNi _x Co _y O ₂
Was good (x + y = 1), and especially LiCoO ₂ was good. Further, good results were obtained even with a positive electrode material in which a part of M was substituted with B, Si, and P.

As the negative electrode active material, an active material capable of inserting and extracting lithium and thermally stable in the presence of a lithium ion conductive nonaqueous electrolyte and an active material can be used. As the negative electrode active material, Li ₄ Ti ₅ O _12, formula _{Li a Cu b Ti c O 4} (0 <a ≦ 1,0 <b ≦ 0.5,
The composite oxide represented by 1.5 ≦ c <2) was good.

[0011] The second component of the negative electrode active material is a battery assembly.
Later, the lithium metal electrically connected to the negative electrode
Therefore, the material is more active than lithium doping of the negative electrode active material.
Need to be preferentially reduced or doped
You. In addition, substances or lithium reduced by lithium
The material doped with um must be thermally stable.
Such materials use lithium metal as a negative electrode and the material as a positive electrode.
It is a substance that can be a lithium primary battery as an electrode.
g, Bi, Co, Cr, Cu, Fe, Mn, Mo, N
b, Ni, Pb, Sb, Se, Sn, Te, Ti, V,
W metal oxide or metal lithium oxide.
Li as negative electrode active material_FourTi_FiveO₁₂, The composition formula Li _aCu_bT
i_cO_Four(0 <a ≦ 1, 0 <b ≦ 0.5, 1.5 ≦ c <2)
When the composite oxide represented by_Two,
Li_TwoCuO_Two, Cu_TwoTiO_ThreeEtc. were particularly good. Book
Even if the substance is added to the negative electrode active material, the synthesis of the negative electrode active material
May remain as unreacted material at the negative electrode
It just needs to be inside.

The amount of lithium to be electrically connected to the negative electrode during assembly is an amount of lithium necessary to reduce the second component of the negative electrode active material or an amount of lithium that can be doped with the second component of the negative electrode active material. Is desirable. When the amount of lithium is larger than the above amount, it tends to be thermally unstable, and when the amount of lithium is smaller than the above amount, the lithium of the positive electrode active material is consumed by the second component of the negative electrode active material, so that the battery capacity decreases. May be.

The electrode is used by compressing a mixture of the positive electrode active material and the negative electrode active material into a pellet shape. Alternatively, a sheet-shaped electrode may be punched and used. The thickness and diameter of the pellet are determined by the size of the battery.

A conductive agent, a binder, a filler, and the like can be added to the electrode mixture. The type of the conductive agent is not particularly limited, and may be a metal powder, but a carbon-based material is particularly preferable. Carbon materials are the most common, and natural graphite (scale graphite, flake graphite, earth graphite, etc.), artificial graphite, carbon black, channel black, thermal black, furnace black, acetylene black, carbon fiber, and the like are used. As the metal, metal powder such as copper, nickel, and silver, and metal fibers are used. Conducting polymers are also used.

As a method for pressing the pellets, a method generally used can be used, but a die pressing method is particularly preferable. The pressing pressure is not particularly limited.
5 ton / cm ² is preferred. Press temperature is from room temperature to 2
00 ° C is preferred.

The amount of carbon added depends on the electric conductivity of the active material, the shape of the electrode and the like, and is not particularly limited. In the case of a negative electrode, the amount is preferably 1 to 50% by weight, particularly preferably 2 to 40% by weight.

The average particle diameter of carbon is 0.5 to 50 μm.
In the range of, preferably in the range of 0.5 to 15 μm, more preferably in the range of 0.5 to 6 μm, the contact between the active materials becomes good, and the formation of a network of electron conduction is improved,
Active materials that do not participate in the electrochemical reaction are reduced.

The binder is preferably insoluble in the electrolytic solution, but is not particularly limited. Usually, polyacrylic acid and neutralized polyacrylic acid, polyvinyl alcohol,
Carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl pyrrolidone, tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene butadiene rubber , Polybutadiene, fluororesin, fluororubber, polyethylene oxide, polyimide, epoxy resin, polysaccharides such as phenolic resin, thermoplastic resin, thermosetting resin, polymer having rubber elasticity, etc. are used alone or as a mixture thereof. The amount of the binder added is not particularly limited, but is preferably 1 to 50% by weight.
In the present invention, when the electrode using polyacrylic acid was heat-treated and used, good results were shown as compared with the others.

As the filler, any fibrous material that does not cause a chemical change in the constructed battery can be used. In the case of the present invention, fibers such as carbon and glass are used. The amount of the filler is not particularly limited,
0-30% by weight is preferred.

As the current collector of the electrode active material, a metal plate having a small electric resistance is preferred. For example, for the positive electrode, in addition to materials such as stainless steel, nickel, aluminum, titanium, tungsten, gold, platinum, and calcined carbon, those obtained by treating the surface of aluminum or stainless steel with carbon, nickel, titanium, or silver are used. Used. For stainless steel, duplex stainless steel is effective against corrosion. In the case of coins and button batteries, nickel plating is performed on the outside of the battery. Examples of the processing method include wet plating, dry plating, CVD, PVD, cladding by pressure bonding, coating, and the like.

For the negative electrode, stainless steel, nickel, copper, titanium, aluminum, tungsten, gold,
In addition to platinum, calcined carbon, and the like, those obtained by treating the surface of copper or stainless steel with carbon, nickel, titanium, or silver, an Al—Cd alloy, or the like is used. Examples of the processing method include wet plating, dry plating, CVD, PVD, cladding by pressure bonding, coating, and the like.

It is also possible to fix the electrode active material and the current collector with a conductive adhesive. As a conductive adhesive,
A resin obtained by adding powder or fiber of carbon or metal to a resin dissolved in a solvent, a resin obtained by dissolving a conductive polymer, or the like is used.

In the case of a pellet-shaped electrode, a conductive adhesive is applied between the current collector and the electrode pellet to fix the electrode.
In this case, the conductive adhesive often contains a thermosetting resin.

A sealant of one or a mixture of asphalt pitch, butyl rubber, fluorinated oil, chlorosulfonated polyethylene, epoxy resin, etc. is used between the gasket and the positive and negative electrode cans. When the sealant is transparent, it is colored to clarify the presence or absence of application. As a method of applying the sealant, injection of the sealant into the gasket,
Coating on positive and negative electrode cans, dipping of gasket into sealant solution, etc.

The use of the coin-type non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but includes, for example, a backup power supply for a cellular phone, a pager, etc., and a power supply for a wristwatch having a power generation function.

The battery of the present invention is desirably assembled in a dehumidified atmosphere or an inert gas atmosphere. It is also preferable that the parts to be assembled are dried in advance. As a method for drying or dehydrating the pellets, sheets and other parts, a generally employed method can be used. In particular, it is preferable to use hot air, vacuum, infrared rays, far-infrared rays, electron beams and low-humidity air alone or in combination. The temperature is preferably in the range of 80 to 350 ° C, particularly 10 ° C.
A range from 0 to 250 ° C is preferred. The water content of the entire battery is preferably 2000 ppm or less, and the positive electrode mixture, the negative electrode mixture and the electrolyte are each preferably 50 ppm or less from the viewpoint of cycleability.

In the battery according to the present invention, the gasket material is not particularly limited, but when assembled as a reflow-compatible battery, the gasket has a heat deformation temperature of 230.
C. or higher is preferred. As the resin material, polyphenylene sulfide resin, polyether ketone resin,
Selected from polyetheretherketone resin, polyethyleneterephthalate resin, polyarylate resin, polybutyleneterephthalate resin, polycyclohexanedimethyleneterephthalate resin, polyethersulfone resin, polyaminobismaleimide resin, polyamideimide resin, polyetherimide resin, and polyamide 46 resin. Preferably, at least one resin is used.

It has been found through experiments that glass fibers, myka whiskers, ceramic fine powder and the like are added to this material in an amount of about 10% by weight or less, and the same effect as in this experiment is exhibited. ing.

[0029]

Embodiment 1 Hereinafter, the present invention will be described in more detail with reference to embodiments.

Example 1 Commercially available LiNiO ₂ was mixed with graphite as a conductive agent and polyacrylic acid resin as a binder at a weight ratio of 90: 8: 2 to prepare an electrode mixture. Next, the electrode mixture was applied at ² ton / cm ² with a diameter of 4 mm and a thickness of 0.6 m.
m into a positive electrode pellet. Next, 5% by weight of commercially available TiO ₂ (anatase type) was mixed with commercially available Li ₄ Ti ₅ O ₁₂ to prepare an electrode mixture as in the case of the positive electrode. Next, the electrode mixture was pressure-formed in the same manner as the positive electrode to obtain a negative electrode pellet having a diameter of 4 mm and a thickness of 0.7 mm. After heat-treating the positive electrode pellet and the negative electrode pellet at 250 ° C., they are respectively adhered to the positive electrode can and the negative electrode can with a conductive adhesive, and an electrolytic solution is injected and sealed on the negative electrode pellet with a lithium metal and glass separator interposed therebetween. Diameter 6.8mm, height 2.1m
m coin-type (button-type) lithium-ion secondary batteries were prepared. Γ-butyrolactone (GBL) as the electrolyte
1 mol / l of lithium borofluoride (LiBF ₄ ) was dissolved in a mixed solvent of ethylene and ethylene carbonate (EC) at a volume ratio of 1: 1. The gasket was made of polyphenyl sulfide resin (PPS). The metallic lithium was attached by calculating the amount doped by the added amount of TiO2 by calculation. After assembling this battery, sufficient aging was performed, and lithium was doped into the negative electrode. Thereafter, reflow soldering was performed so that the surface temperature of the negative electrode can becomes the temperature transition shown in FIG. 1, and the battery voltage (Eo) and the AC internal resistance (Riac, 1 KHz) before and after the reflow were measured.

As Comparative Example 1, the electrode material of the negative electrode was Li ₄
It has created a battery that is the only Ti ₅ O _12. Since this battery has no voltage after assembly, it is charged after charging at 3.3 V for 3 minutes.
Those left for days were used.

Table 1 shows the measurement results.

[0033]

[Table 1]

As shown in Table 1, in the battery of the present invention, the battery voltage (Eo) and the battery internal resistance (Riac) hardly changed before and after reflow, and no deterioration in battery characteristics was observed.
On the other hand, in Comparative Example 1, before and after reflow, the battery voltage dropped (E
o) and an increase in the battery internal resistance (Riac) are observed, and the battery swells after reflow. In Comparative Example 1, battery characteristics were clearly degraded, which is presumed to be due to decomposition of the electrolytic solution.

Example 2 LiCo was used as the positive electrode active material.
O_TwoAnd a positive electrode pellet was prepared in the same manner as in Example 1.
Was. Mixing lithium hydroxide with titanium oxide and copper powder
It was fired to obtain a powder. XRD analysis of this powder and this powder
Results of measuring the capacity of a single lithium battery prepared separately using
As a result, this powder is LiCu_0.5Ti_1.5O_FourIs the main component,
TiO_Two, Li _TwoCuO_Two, Cu_TwoTiO_ThreeAbout 3% remaining
I knew I was doing it. This powder was used as the negative electrode mixture,
A battery was prepared in the same manner as in Example 1. Metallic lithium remains
TiO _Two, Li_TwoCuO_Two, Cu_TwoTiO_ThreeEtc.
Measurement of lithium monopolar battery with separately created ping volume
Of the relevant amount, half of the relevant amount, and
1.5 times the amount was stuck.

After assembling the battery, the battery is sufficiently aged,
Lithium was doped into the negative electrode. Thereafter, reflow soldering is performed so that the surface temperature of the negative electrode can becomes the temperature transition shown in FIG. 1, and the battery voltage (Eo) and the AC internal resistance (Riac, 1 KHz) before and after the reflow, and the electric capacity (C, 3.3 V). Charge for 24 hours, 3.3 at 25 μA
2.0 V discharge).

Table 2 shows the measurement results.

[0038]

[Table 2]

In Table 2, the capacity when the amount of lithium is set to half the amount of lithium is smaller than the capacity when the amount of lithium is the amount of lithium. This is because in the first discharge, the second component of the negative electrode active material is doped with lithium and consumed, and lithium in the battery used for the battery capacity is reduced. On the other hand, the amount of lithium is set to 1.
When the amount is 5 times, the change in the AC internal resistance (Riac) and the change in the battery voltage (Eo) before and after reflow are larger than those of the battery having the corresponding amount of lithium. This is because lithium remains in the battery even after doping, and a reaction such as reduction of the electrolytic solution occurs by the reflow heat treatment, thereby deteriorating the battery characteristics. Therefore, in the present invention, it is desirable to attach lithium corresponding to the amount to the negative electrode.

[0040]

As described above, a lithium ion conductive non-aqueous electrolyte and a heat-resistant gasket are used, LiMO ₂ (M is Co, Ni) as a positive electrode active material, and titanium having a spinel structure as a negative electrode active material. lithium or composition formula _{Li a Cu b Ti c O 4} (0 <a ≦ 1,0 ≦ b ≦ 0.
5, 1.5 ≦ c <2), and the negative electrode contains a metal oxide composed of Li, Cu, and Ti. Further, when assembling the battery, the metallic lithium is applied to the negative electrode. The non-aqueous electrolyte coin-type secondary battery assembled according to the present invention, which is characterized in that it is electrically connected, has no characteristic deterioration due to reflow soldering. Further, since the battery of the present invention has a battery voltage even after reflow soldering, a simple method of measuring the battery voltage can be adopted for an electrical contact between the battery and the substrate or a characteristic deterioration test of the battery.

[Brief description of the drawings]

FIG. 1 is a diagram showing a substrate surface temperature during reflow soldering.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shunji Watanabe 5-30-1, Nishitaga, Taihaku-ku, Sendai City, Miyagi Prefecture Inside SII Micro Parts Co., Ltd. (72) Inventor Shinichi Takasugi Nishitaga, Taishiro-ku, Sendai City, Miyagi Prefecture 5-30-1 SII Micro Parts Co., Ltd. (72) Inventor Sakai Tsuguo 5-30-1, Nishitaga, Taishiro-ku, Sendai City, Miyagi Prefecture S-II Micro Parts Co., Ltd. F-term (reference) 5H011 AA02 CC06 FF03 HH02 KK04 5H029 AJ04 AK03 AL02 AL03 AM03 AM05 AM07 BJ03 CJ28 DJ03 HJ02 HJ14 5H050 AA10 BA17 CA08 CB02 CB03 HA02 HA14

Claims (2)

[Claims] 1. LiMO ₂ (M is C
o, using Ni), as an anode active material, lithium titanate or composition formula having a spinel structure Li _a Cu _b Ti _c
Using a composite oxide lithium represented by O ₄ (0 <a ≦ 1, 0 ≦ b ≦ 0.5, 1.5 ≦ c <2), at least comprising a lithium ion conductive non-aqueous electrolyte and a heat-resistant gasket In the non-aqueous electrolyte coin-type secondary battery, a metal oxide containing at least one or more metals selected from Cu and Ti in the negative electrode, or a metal containing at least one or more metals selected from Cu and Ti and Li A non-aqueous electrolyte secondary battery comprising lithium oxide, wherein metallic lithium is electrically connected to a negative electrode when the battery is assembled. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein a gasket made of a resin having a heat distortion temperature of 230 ° C. or higher is used as a member.