JP2000173664A - Power source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a cycle characteristic by arranging a cooling system in a nonaqueous secondary battery, having a negative electrode substance capable of storing/releasing a lithium ion, a positive electrode substance composed of lithium, containing composite oxide capable of storing/releasing a lithium ion and a lithium ion conductive nonaqueous electrolyte. SOLUTION: A cooling method does not cool a circuit inside a power source device, but selectively cools a battery can attached to the power source device, to thereby actively prevent a temperature rise in the battery can to effectively prevent the cycle degradation at high temperature time seen in a lithium ion secondary battery, particularly, a lithium ion secondary battery using lithium manganate as a positive electrode active material to maintain performance of the battery. For example, an aluminum cooling jacket 4 is installed on the periphery of the battery can, a refrigerant is sent into from a filler hole 5 of the refrigerant, and is discharged from a discharge port 6 of the refrigerant to cool battery can. When the temperature sensor is controlled by being installed in a cooler, energy can be reduced, and supercooling can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a power supply device provided with a cooling device for cooling a secondary battery.

[0002]

2. Description of the Related Art In recent years, along with the development of electronic portable devices, there has been a remarkable progress in the development of batteries as driving sources thereof. Among them, lithium ion secondary batteries have attracted particular attention because of their high energy density.

At present, commercially available lithium ion secondary batteries use a material capable of reversibly inserting and extracting lithium, such as a carbon material, an amorphous alloy, or an amorphous metal oxide, as a negative electrode active material. The substance is cobalt,
Using a lithium composite oxide containing a transition metal such as nickel or manganese, a mechanism is employed in which lithium ions move between the two electrodes to perform charging and discharging. The active material used for both electrodes has a high energy density, so that the battery can be reduced in size and weight. For this reason, lithium ion secondary batteries have been downsized,
It has been increasingly used for portable devices such as a camera-integrated VTR or a mobile phone for which weight reduction is desired.

[0004] More recently, attempts have been made to use lithium ion secondary batteries not only in portable equipment but also in medium- and large-sized power supplies. Medium- and large-sized power supplies are used as power supplies for driving motors of electric vehicles and bicycles with electric motors, load levelers that are energy storage devices for home use, backup power supplies for offices that handle a large amount of communication equipment and OA equipment, etc. It has a wide range of applications, including large-volume laboratories and power storage devices attached to private power generators at factories. However, lithium ion secondary batteries currently in practical use show a tendency that the electric capacity decreases as charging and discharging are repeated. This phenomenon called cycle deterioration shortens the life of the battery and causes a reduction in cost performance.

Various theories have been proposed as to the cause of the cycle deterioration, such as the theory that it is caused by the transformation of the positive electrode active material due to charge and discharge, the theory that it is caused by the transformation of the negative electrode active material, and the theory that it is caused by the deterioration of the electrolytic solution. However, details have not been disclosed. However, as a tendency observed in the whole lithium ion secondary battery, it is known that when the temperature at the time of charging and discharging increases, the cycle deterioration increases. This is presumed to be due to a certain chemical reaction that causes the cycle deterioration, and that the frequency of the reaction increases as the temperature increases.

The transformation of the positive electrode active material, which is considered as one of the causes of cycle deterioration, is particularly susceptible to temperature. A lithium composite oxide containing a transition metal such as cobalt, nickel, and manganese is mainly used for a positive electrode of a current lithium ion secondary battery. It is known that these lithium composite oxides gradually dissolve in a non-aqueous electrolyte and elute lithium and transition metals forming the basic skeleton of the active material, which directly reduce the capacity of the positive electrode. Cause. Further, this phenomenon is largely affected by the temperature because it is basically a dissolution phenomenon, resulting in a decrease in the electric capacity of the battery not only when the battery is stored at a high temperature but also when the battery is stored at a high temperature. .

The above phenomenon is particularly remarkable in a lithium composite oxide containing manganese. It is considered that this is because the binding between manganese and oxygen in the oxide crystal is weak, and it is experimentally known that the dissolution in the non-aqueous electrolyte at high temperatures becomes severe. Lithium composite oxides containing manganese are less expensive than lithium composite oxides containing other transition metals, and the reserves of manganese are more sufficient than those of cobalt. It is expected to replace the current cobalt-containing lithium composite oxide as a positive electrode active material.

In order to avoid this difficulty, various methods have been proposed so far. In particular, for lithium manganate, which is a lithium composite oxide containing manganese, the raw material ratio at the time of calcination is adjusted to lithium manganate having a stoichiometric composition to make the composition excessive in lithium, thereby improving high-temperature characteristics. A method for improving the high-temperature characteristics by adding a transition metal element other than manganese to increase the stability of the spinel crystal constituting the active material (Japanese Patent Laid-Open No. 3-219571). ) Has been proposed.

However, in these methods, in order to obtain an active material that is uniform and does not generate a subphase, the adjustment of raw materials and the adjustment of firing conditions must be precisely controlled, and the production process of the active material becomes complicated. In addition, there is a disadvantage that the electric capacity of the battery is reduced. Further, the active material obtained in this way shows superior high-temperature characteristics to lithium manganate having a stoichiometric composition, but cannot be said to have practically sufficient high-temperature stability. In particular, when the battery has a large electric capacity such as a medium-sized or large-sized power supply, the heat generated by charging and discharging is large. The development of a solution was desired.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a power supply having excellent cycle characteristics.

[0011]

Means for Solving the Problems The inventors of the present invention have been studying to solve the above problems, and in a power supply device using a lithium ion secondary battery, a power supply device having the following configuration has excellent cycle characteristics. It was found that. That is, the present invention provides (1) a negative electrode active material capable of inserting and extracting lithium ions, a positive electrode active material comprising a lithium-containing composite oxide capable of inserting and extracting lithium ions, and a lithium ion conductive nonaqueous electrolyte. A non-aqueous secondary battery provided with a cooling device for cooling the secondary battery, (2) a lithium-containing composite oxide capable of inserting and extracting lithium ions The power supply device according to (1), wherein the positive electrode active material is a lithium composite oxide containing manganese.

The present invention relates to a power supply device comprising a lithium ion secondary battery and a cooling device for preventing the temperature of the battery can from increasing during charging / discharging and storage of the battery. . This is not to solve the cycle deterioration phenomenon at high temperature in lithium ion secondary batteries by improving the components inside the battery, but to prevent it by raising the battery temperature when using the battery. Is based on the idea that it is efficient and reliable.

The cooling device according to the present invention does not cool the circuit inside the power supply device as seen in a general power supply device using a battery, but selectively cools a battery can attached to the power supply device. There are features. This positively prevents the temperature of the battery can from rising, effectively preventing the cycle deterioration at high temperatures seen in lithium-ion secondary batteries, especially lithium-ion secondary batteries using lithium manganate as a positive electrode active material. Thus, the performance of the battery can be maintained.

In the present invention, examples of the negative electrode active material capable of inserting and extracting lithium ions include lithium metals, lithium alloys, metal oxides, metal nitrides, alloys, and intermetallic compounds. In particular, examples of the carbon-based material include carbon materials, such as coke, natural graphite, artificial graphite, and non-graphitizable carbon, which are currently generally used as a negative electrode of a lithium ion secondary battery or a mixture thereof.

The positive electrode active material comprising a lithium-containing composite oxide capable of inserting and extracting lithium ions includes lithium cobaltate, lithium manganate, lithium nickelate,
Elements different from the main metal elements constituting the crystal structure of these lithium composite oxides (for example, nickel, chromium,
Cobalt, copper, aluminum, vanadium, magnesium, strontium, iron, boron, chlorine, fluorine, bromine, iodine, etc.) or a mixture of two or more of these lithium composite oxides can give. Further, as described above, among these lithium-containing composite oxides, the present invention is particularly effective for lithium-containing composite oxides containing manganese.

The lithium ion conductive non-aqueous electrolyte is
It refers to a lithium salt dissolved in a non-aqueous solvent. Here, as the lithium salt, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ or the like, or a mixture thereof is used. As the solvent, an organic solvent or an inorganic solvent that dissolves the lithium salt can be used, and particularly preferably, ethylene carbonate, propylene carbonate, diethyl carbonate,
It is recommended to use a solvent such as dimethyl carbonate, methyl ethyl carbonate, gamma butyl lactone alone or in a mixture. The appropriate concentration of the lithium salt dissolved in the solvent is 0.5 to 2.0 mol / liter.

In the present invention, the non-aqueous secondary battery is composed of a negative electrode active material capable of inserting and extracting lithium ions and a lithium-containing composite oxide capable of inserting and extracting lithium ions as described above. In addition to the positive electrode active material and the lithium ion conductive non-aqueous electrolyte, a metal current collector holding the positive and negative electrode active materials, an electrode tab for conductivity, and a separator for electrically separating the positive and negative electrodes , And a battery can containing these components, and other battery members such as a current cutoff valve. Examples of the shape of the battery include a cylindrical shape, a square shape, a thin square shape, a card shape, a coin shape, a sheet shape, and the like. The present invention is effective for any shape of the battery.

In the present invention, the cooling device for cooling the secondary battery selectively cools the battery so that the battery temperature does not rise above a certain temperature.
The method of cooling is not particularly limited, but an air-cooling type in which air is forcibly fed and cooled, a method in which a jacket is attached to a battery, and a system in which a coolant such as water is passed therethrough for cooling are simple and effective. Recommended as a method. In addition, a method in which heat is exchanged by electric energy using a suitable refrigerant and a heat exchanger to forcibly cool the battery portion is expensive, but is recommended as a reliable method. In addition, if these coolers are equipped with temperature sensors that sense the temperature of the battery and start and stop the cooler, unnecessary energy consumption during cooling can be suppressed and the battery can be prevented from being overcooled. And is particularly recommended.

[0019]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the scope of the present invention is limited thereto. Example 1 Lithium manganate, polyvinylidene fluoride, and acetylene black were mixed in a weight ratio of 100 parts, 4 parts, and 6.25 parts, and dissolved in N-methylpyrrolidone to form a slurry. This was applied to a 15-micron thick aluminum foil using a coating die coater, and then dried to obtain a positive electrode. Graphite, carboxymethylcellulose, and styrene / butadiene latex were mixed at a weight ratio of 100 parts, 1 part, and 2 parts, and dissolved in water to form a slurry. This one
It was applied to a 5 μm thick copper foil in the same manner as the positive electrode and dried to obtain a negative electrode. The positive electrode and the negative electrode were cut into a rectangle of 20 cm × 30 cm, and an electrode terminal for current collection was welded to each. Next, the polyethylene porous separator was cut into 22 cm × 32 cm, and was sandwiched between a positive electrode and a negative electrode to form one unit, and 10 layers were stacked.
After being stored in an aluminum battery can case measuring 3 cm x 33 cm x 2 cm, the electrolyte was mixed with 1 mol / L LiPF ₆ and the solvent was 1: 1 by volume ratio of ethylene carbonate and methyl ethyl carbonate. Liquid)
The injection port was welded to seal the battery can.

An aluminum cooling jacket was attached to the periphery of the battery so that air could be blown into the jacket from a blower with wings attached to a DC motor. 4. After starting the ventilation, charge the battery at a charging voltage of 4.2 V for 8 hours.
A charge / discharge cycle of discharging to 2.7 V at 0 A was repeated 100 times. At this time, the surface temperature of the battery at the beginning and end of the charge / discharge cycle, and the discharge amount maintenance rate expressed by the following equation, which represents the degree of cycle deterioration, was calculated.
As shown in Table 1, good cycle characteristics were exhibited. Discharge rate maintenance rate (%) = [1- (100th cycle discharge rate)
/ Discharge amount in first cycle)] × 100 Example 2 A battery was produced in the same manner as in Example 1. An aluminum water-cooled jacket equipped with a water tank and a pump was attached around the battery can. A charge / discharge cycle test was performed in the same manner as in Example 1 while operating the pump to supply water. When the surface temperature of the battery at the beginning and end of the charge / discharge cycle and the discharge amount maintenance ratio were calculated, the results were as shown in Table 1, and excellent cycle characteristics were exhibited.

Example 3 A battery was manufactured in the same manner as in Example 1. An aluminum water-cooled jacket equipped with a water tank and a pump was attached around the battery can. A throw-in type cooler equipped with a thermometer was attached to the water tank. A charge / discharge cycle test was performed in the same manner as in Example 1 while setting the water temperature to 30 degrees, operating the cooler and the pump, and keeping the temperature of the water supplied to the jacket at 30 degrees. When the surface temperature of the battery at the beginning and end of the charge / discharge cycle and the discharge amount maintenance ratio were calculated, the results were as shown in Table 1, and favorable cycle characteristics were exhibited. Example 4 A battery was produced in the same manner as in Example 1, except that lithium cobaltate was used instead of lithium manganate as the positive electrode active material. After starting to blow air, charge the battery at 4.2V
For 8 hours, and a charge / discharge cycle of discharging at 5.0 A to 2.7 V was repeated 100 times. At this time,
When the surface temperature and the discharge amount maintenance rate of the battery at the beginning and end of the charge / discharge cycle were calculated, the results were as shown in Table 1, and excellent cycle characteristics were shown.

Example 5 A battery was fabricated in the same manner as in Example 1 except that lithium cobaltate was used instead of lithium manganate as the positive electrode active material. As in Example 2, an aluminum water-cooled jacket equipped with a water tank and a pump was attached around the battery can. Example 1 while operating the pump to supply water
A charge / discharge cycle test was performed in the same manner as described above. When the surface temperature of the battery at the beginning and end of the charge / discharge cycle and the discharge amount maintenance ratio were calculated, the results were as shown in Table 1, and excellent cycle characteristics were exhibited. Example 6 A battery was produced in the same manner as in Example 1, except that lithium cobaltate was used instead of lithium manganate as the positive electrode active material. As in Example 3, an aluminum water-cooled jacket equipped with a water tank and a pump was attached around the battery can. A throw-in type cooler equipped with a thermometer was attached to the water tank. A charge / discharge cycle test was performed in the same manner as in Example 1 while setting the water temperature to 30 degrees, operating the cooler and the pump, and keeping the temperature of the water supplied to the jacket at 30 degrees. When the surface temperature of the battery at the beginning and end of the charge / discharge cycle and the discharge amount maintenance ratio were calculated, the results were as shown in Table 1, and excellent cycle characteristics were exhibited.

COMPARATIVE EXAMPLE 1 A battery prepared in the same manner as in Example 1 was subjected to a charge / discharge cycle test in the same manner as in Example 1 without installing a cooler for cooling the battery can. When the surface temperature and the discharge amount maintenance ratio were calculated, Table 1 was obtained.
It became like. It can be seen that the temperature rise of the battery can is larger and the discharge capacity retention ratio is smaller than when the cooling device is attached. Comparative Example 2 A battery prepared in the same manner as in Example 4 was subjected to a charge / discharge cycle test in the same manner as in Example 4 without attaching a cooler for cooling the battery can, and the surface temperature of the battery at the beginning and end of the charge / discharge cycle, And the discharge maintenance rate was calculated.
It became like. It can be seen that the temperature rise of the battery can is larger and the discharge capacity retention ratio is smaller than in the case where the cooling device is attached.

[0024]

[Table 1]

[0025]

According to the present invention, by using a power supply device having a cooling device for cooling a lithium ion secondary battery, it is possible to prevent a temperature rise of the battery and exhibit good cycle characteristics. Can be.

[Brief description of the drawings]

FIG. 1 shows a battery can according to an embodiment of the present invention.

FIG. 2 shows a state where a cooling jacket is attached around the battery can of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery can 2, 3 Current collecting terminal 4 Cooling jacket 5 Refrigerant inlet 6 Refrigerant outlet

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5H029 AJ03 AJ05 AK03 AL01 AL02 AL06 AL07 AL12 AM03 AM05 AM07 BJ03 BJ04 BJ22 5H031 AA00 CC05 EE01 EE02 EE03 KK00 KK03 KK08

Claims (2)

[Claims] 1. A negative electrode active material capable of inserting and extracting lithium ions, a positive electrode active material comprising a lithium-containing composite oxide capable of inserting and extracting lithium ions, and a lithium ion conductive nonaqueous electrolyte. A power supply device, wherein a cooling device for cooling the non-aqueous secondary battery is attached to the non-aqueous secondary battery. 2. The positive electrode active material comprising a lithium-containing composite oxide capable of inserting and extracting lithium ions is a manganese-containing lithium composite oxide.
The power supply device according to claim 1.