JP2003217687A - Lithium ion battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain deterioration of a battery when a lithium ion battery is stored at high temperatures. <P>SOLUTION: In this lithium battery, a battery temperature detecting sensor is provided on the surface of the lithium battery. The battery is provided with a residual capacity discharging control means for discharging until the voltage of the battery reaches a predetermined voltage in the case where the battery is not in the course of charging or discharging when the temperature detected by the battery temperature detecting sensor reaches a predetermined temperature or more. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion battery used as a power source for various portable devices and moving objects, and a means for controlling remaining capacity discharge. The present invention relates to a lithium ion battery provided with. 2. Description of the Related Art A non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, which is a small, large-capacity sealed battery, is used as a power source for portable telephones, notebook computers, camcorders, and the like. . These non-aqueous electrolyte secondary batteries have a large volume capacity density, a large weight capacity density, and the like, and are capable of extracting a high voltage. It is expected to be used not only for power supplies for equipment but also for power sources such as electric assist bicycles, electric wheelchairs, and electric vehicles. A lithium ion secondary battery has a negative electrode using an active material such as a carbonaceous material capable of doping and undoping lithium and a positive electrode using a composite oxide of lithium and a transition metal oxide as an active material. A battery element obtained by coating the negative electrode side current collector and the positive electrode current collector and laminating them via a separator is coated with an exterior material, or a battery element in which these are spirally wound inside a battery can. To manufacture batteries. [0004] As a positive electrode active material of a lithium ion secondary battery, a lithium cobalt composite oxide and a lithium manganese composite oxide are used. Manganese is much more abundant than cobalt as a resource, and a battery using a lithium manganese composite oxide as a positive electrode active material has a higher capacity than a battery using a lithium cobalt composite oxide as a positive electrode active material.
It has a feature of high safety even when an abnormal reaction occurs due to a short-circuit of a battery terminal or the like, and is particularly suitable for a large-sized battery. [0005] Lithium-ion batteries are known as batteries with little deterioration in charge capacity. However, there is a problem that deterioration when stored in a charged state is large.
It is pointed out in Japanese Patent Application Publication No. 00-287372 that it is proposed that when a time during which charging or discharging is not performed continues for a predetermined time, the lithium ion secondary battery is discharged and then the lithium ion secondary battery is left. . [0006] When the leaving of the lithium ion battery in the charged state was examined in detail, the deterioration of the battery capacity due to the leaving of the lithium ion battery in the charged state was as follows.
It became clear that the higher the temperature, the larger the storage. In addition, it has become apparent that batteries containing a lithium manganese composite oxide as the positive electrode active material have a greater tendency than batteries using a lithium cobalt composite oxide or the like. SUMMARY OF THE INVENTION An object of the present invention is to prevent a phenomenon in which the capacity of a lithium ion battery is deteriorated when it is left in a charged state. Another object of the present invention is to solve the problem of capacity deterioration in a battery containing a lithium manganese composite oxide as a positive electrode active material. SUMMARY OF THE INVENTION An object of the present invention is to provide a lithium ion battery having a battery temperature detection sensor on the surface of the lithium ion battery, wherein the temperature detected by the battery temperature detection sensor is a predetermined temperature. A lithium ion battery provided with a remaining capacity discharge control means for performing discharge until the voltage of the battery reaches a predetermined voltage when the battery is not charging or discharging when the above is reached. The above-mentioned lithium-ion battery, wherein the lithium-ion battery is a lithium-manganese battery. In a method of using a lithium ion battery,
When the temperature of the lithium battery becomes equal to or higher than a predetermined temperature, whether or not the lithium ion battery is being charged or discharged is detected. If not, the remaining capacity discharge is performed until the battery voltage drops to a predetermined voltage. This is a method of using a lithium ion battery that discharges the battery by operating the control means. Further, there is provided a method for using the above-mentioned lithium ion battery, wherein the lithium ion battery is a lithium manganese battery. This is a method for using the lithium ion battery, which discharges the remaining capacity when the battery temperature is 40 ° C. or higher. This is a method for using the above-mentioned lithium ion battery, which discharges the battery voltage to 2.5 V to 3.5 V. In a battery pack having a lithium ion battery, the battery pack has a battery temperature detection sensor and a remaining capacity discharge control means, and when the battery temperature detected by the battery temperature detection sensor is equal to or higher than a predetermined temperature, the battery is charged. A battery pack having remaining capacity discharge control means for supplying current to a discharge resistor until the voltage of the battery reaches a predetermined voltage when not discharging. In the above battery pack, the remaining capacity discharge control means is provided in the battery charge / discharge control means. In the above battery pack, the lithium ion battery is a lithium manganese battery. In a battery-powered apparatus using a lithium-ion battery as a power source, the battery-powered device includes a battery temperature detection sensor and a remaining capacity discharge control means. When the battery temperature detected by the battery temperature detection sensor is equal to or higher than a predetermined temperature, The battery-equipped device includes a remaining capacity discharge control unit that supplies current to a discharge resistor until the voltage of the battery reaches a predetermined voltage when the battery is not charging or discharging. In the battery-equipped device, the remaining capacity discharge control means is provided in the battery charge / discharge control means. The battery-using device as described above, wherein the lithium ion battery is a lithium manganese battery. DETAILED DESCRIPTION OF THE INVENTION The present invention has been found to be able to solve the capacity deterioration phenomenon during storage in a lithium ion battery by discharging the remaining capacity of the lithium ion battery. In particular, they have been found to be effective in preventing the capacity degradation phenomenon when stored at a high temperature. The reason why the capacity deterioration phenomenon during storage in a lithium ion battery can be prevented by discharging the battery voltage to a predetermined voltage is not clear, but the decrease in the battery voltage causes the non-aqueous solvent electrolyte to lose its capacity. It is supposed that decomposition or the like is suppressed, or that dissolution or the like of the positive electrode active material is suppressed. The present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating an embodiment of the lithium ion battery of the present invention. The lithium ion battery 1 is provided with a battery temperature sensor 2 for measuring the battery temperature on the surface of the battery.
Is bound to The discharge control means 2 is connected to a battery current detection means 4 and a battery voltage detection means 5, and detects a current flowing between the battery and an external circuit and a battery voltage. Further, the remaining capacity discharge control means 3 includes:
An external connection terminal 7 is connected to a discharge resistor 6 to which a discharge current is supplied, and is connected to a device using a battery or a charger.
have. When it is detected from the output of the battery current detecting means 4 that neither charging nor discharging of the battery is performed, the battery temperature is detected by the battery temperature sensor 2. When the battery temperature is equal to or higher than a predetermined temperature, the remaining capacity discharge control means 3 applies a current to the discharge resistor 6 to discharge the amount of electricity stored in the battery. Then, at the time of discharging, the battery voltage is detected by the battery voltage detecting means 5 so that the battery voltage does not fall below the discharge stop voltage so as not to be in an overdischarge state. Further, when the current is supplied to the discharge resistor 6 by the operation of the current discharging means and the current supply to the battery using equipment or the charging of the battery is started, the battery current detecting means 4
As a result, the current is detected, and the current supply to the discharge resistor 6 is stopped. As described above, when the battery temperature during storage becomes equal to or higher than the predetermined temperature, current is supplied to the discharge resistor up to the predetermined voltage, thereby preventing deterioration of the charge / discharge capacity of the battery. It is possible to do. In the case where the lithium ion battery provided with the battery remaining capacity discharge control means of the present invention is a battery provided in a battery pack, a battery temperature sensor is provided on the surface of the battery in the battery pack, and the remaining capacity discharge is provided. The control means may be provided in the battery pack together with the battery charge / discharge control means. Alternatively, only the battery temperature sensor may be provided on the battery surface, and each unit including the battery discharge control unit may be provided inside the charge / discharge control device, or may be provided on the side of the device using the battery. The battery discharge circuit of the present invention has a battery temperature of 4
It is preferable to discharge when the temperature reaches 0 ° C to 50 ° C. If the temperature is set to a temperature lower than 40 ° C, the temperature rise of the battery-powered equipment, and even a slight temperature rise during storage is preferable, so that it is preferable. Absent. On the other hand, when the operation start temperature is set to a temperature higher than 50 ° C., the effect of suppressing deterioration of the battery during storage becomes small. Further, it is preferable that the discharge of the remaining capacity is stopped when the terminal voltage of the battery reaches 2.5 V to 3.5 V. If the discharge voltage is higher than this, the battery is overdischarged and the characteristics of the lithium ion battery are greatly deteriorated. I do. The lithium ion battery of the present invention is suitable for preventing deterioration during storage of a battery containing a lithium manganese composite oxide as a positive electrode active material, and Li _{1 + x} Mn ₂ as a lithium manganese composite oxide. _-x O ₄ (0 &#60; X ≦
0.15) is particularly suitable for preventing battery deterioration. In addition, a lithium cobalt composite oxide, a lithium nickel composite oxide, a lithium nickel cobalt oxide (LiNi
_1-x Co _x O ₂ ). Examples of the negative electrode include graphite (graphite), non-graphitizable carbon (hard carbon), easily graphitizable carbon (soft carbon), and carbon black, and a mixture thereof can be used. In the non-aqueous electrolytic solution used in the present invention, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, methyl propyl carbonate, vinylene Examples include at least one selected from carbonate, gamma-butyrolactone, methyl propionate, and ethyl propionate. Among them, a mixed solvent containing ethylene carbonate and diethyl carbonate is preferable because it has a high dielectric constant and a low viscosity.
The supporting electrolytes used for preparing the non-aqueous electrolyte include LiPF ₆ , LiBF ₄ , LiClO ₄ , and LiN (S
O ₂ C ₂ F ₅ ) _{2 and the} like. The present invention will be described below with reference to examples and comparative examples. Example 1 (Production of Battery) Width 58 mm, length 502 mm, thickness 20
Lithium manganese composite oxide (Li _{1 + x} Mn _2-x O ₄ x =
0.10) Powder: A mixture of 92 parts by weight, 5 parts by weight of conductivity-imparting carbon, and 3 parts by weight of polyvinylidene fluoride is applied so that the thickness after drying including aluminum foil is 164 μm after press molding, and the positive electrode And The negative electrode was composed of 90.5 parts by weight of graphite powder on both sides of a copper foil having a width of 59 mm, a length of 483 mm and a thickness of 10 μm.
It was prepared by applying a mixture comprising 0.5 parts by weight of carbon black and 9 parts by weight of polyvinylidene fluoride so as to have a dry thickness of 111 μm after press molding including a copper foil. Laminating microporous polyethylene membrane separator / positive electrode / microporous polyethylene membrane separator / negative electrode in this order,
The battery element was produced by spirally winding and housed in a battery can. In a battery can, a mixed solvent consisting of 30 parts by volume of ethylene carbonate and 70 parts by volume of diethyl carbonate was added with L
An electrolytic solution dissolved so that the concentration of iPF ₆ was 1.0 M was injected and sealed, thereby producing a lithium ion secondary battery. A circuit board provided with a battery temperature detection sensor, a remaining capacity discharge control unit, a battery voltage detection unit, a current detection unit, and a discharge resistor was mounted on the manufactured battery. The lithium ion battery was charged at a constant current up to a terminal voltage of 4.2 V, was switched from 4.2 V to a constant voltage charge, and the charging was completed in 2.5 hours from the start of the constant current charge to a total charge time. In the fully charged state, when the battery temperature reaches 50 ° C., the residual capacity discharging means which discharges to 3.3 V is operated, and after storing at 20 ° C., 45 ° C. and 60 ° C. for 4 weeks, each battery is re-charged. Charge and measure the discharge capacity,
The ratio of each capacity to the initial capacity is shown in FIG. 2 as the capacity maintenance rate. 96.2 stored at 45 ° C.
%, But those stored at 60 ° C. had a capacity retention of 101.1%. Further, for comparison, the capacity retention ratio was also measured for a battery stored in a completely discharged state. 102.8% at 20 ° C storage, 102.3% at 45 ° C storage.
%, And 101.7% when stored at 60 ° C.
It was shown to. Example 2 The capacity retention was shown as Example 2 in FIG. 2 in the same manner as in Example 1 except that when the battery temperature reached 40 ° C., the residual capacity discharging means was activated. The capacity retention rate during storage at 45 ° C. reached 101.9%. Comparative Example 1 Example 1 except that the residual capacity discharging means was not operated.
The capacity retention ratio is shown in FIG. When stored at 45 ° C., the capacity retention decreased to 96.1%,
At ℃, it dropped to 85.2%. As shown in FIG. 2, at 20 ° C., almost no capacity deterioration was observed.
Rather, the capacity retention rate increased during storage, which may be due to the better penetration of the electrolyte into the electrodes during storage. The lithium ion battery of the present invention is provided with a remaining capacity discharging means for discharging the remaining capacity when exposed to a high temperature during storage, thereby preventing deterioration of the active material during storage. Therefore, even if the battery is stored at a high temperature, deterioration of the charge capacity can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a lithium ion battery of the present invention. FIG. 2 is a diagram illustrating an example of the present invention and a comparative example. [Description of Signs] 1 ... Lithium ion battery, 2 ... Battery temperature sensor, 3 ...
Remaining capacity discharge control means, 4 ... battery current detection means, 5 ... battery voltage detection means, 6 ... discharge resistance, 7 ... external connection terminal

Claims (1)

Claims: 1. A lithium-ion battery, comprising: a battery temperature detection sensor on a surface of the lithium-ion battery; when a temperature detected by the battery temperature detection sensor reaches a predetermined temperature or higher, A lithium ion battery provided with a remaining capacity discharge control means for discharging the battery until the battery voltage reaches a predetermined voltage when the battery is not charging or discharging.