JP2003036890A - Nonaqueous electrolytic solution secondary battery and electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution secondary battery, of which the decrease of capacity and output resulting from charge/discharge cycles can be suppressed to make the life of the battery long. SOLUTION: A cylindrical lithium ion battery is manufactured, using manganese acid lithium or cobalt acid lithium for a positive electrode and amorphous carbon powder or graphite powder for a negative electrode. In the manufactured battery, the ratio of an internal resistance for 85% of DOD(depth of discharge) is made lower than 150% to that for 0% of DOC. In this manner, the differences between respective internal resistances can be made small in the whole range of charge and discharge for practical applications, so that the discharge efficiency of the battery can be improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a positive electrode using a lithium transition metal complex oxide as a positive electrode active material and a negative electrode using a carbon material as a negative electrode active material. The present invention relates to a non-aqueous electrolyte secondary battery in which a group of electrodes is infiltrated with a non-aqueous electrolyte and accommodated in a battery container, and an electric vehicle.

[0002]

2. Description of the Related Art Lithium ion secondary batteries, which are representative of non-aqueous electrolyte secondary batteries, are mainly used for powering portable devices such as VTR cameras, laptop computers, and mobile phones by taking advantage of their high energy density. Has been done. The internal structure of this battery is usually of the wound type as shown below. Both the positive electrode and the negative electrode have a strip shape in which the active material is applied to the metal foil, and the cross section is spirally wound to form a winding group so that the positive electrode and the negative electrode do not come into direct contact with each other with the separator interposed therebetween. . This winding group is housed in a cylindrical battery can that serves as a battery container, and after the electrolytic solution is injected, it is sealed.

A general cylindrical lithium ion secondary battery is called 18650 type having a diameter of 18 mm and a height of 65 mm, and is widely used as a small-sized consumer lithium ion battery. Lithium cobalt oxide, which is characterized by high capacity and long life, is mainly used for the positive electrode active material of 18650 type lithium ion secondary battery, the battery capacity is about 1.3 Ah to 1.8 Ah, and the output is about 10 W. It is a degree.

On the other hand, in the automobile industry, in order to cope with environmental problems, an electric vehicle without exhaust gas, which uses only a battery as a power source, and a hybrid which uses both an internal combustion engine and a battery as power sources ( The development of electric vehicles has accelerated, and some of them are in the stage of practical application.

Naturally, a battery serving as a power source of an electric vehicle is required to have a characteristic that a high output and a high energy can be obtained, and a lithium ion battery attracts attention as a battery which meets the requirement. In order to popularize electric vehicles, it is essential to reduce the cost of batteries, and low-cost battery materials are required for that purpose. Has received particular attention, and improvements aimed at improving the performance of batteries have been made. In addition, not only high capacity but also high output that influences acceleration performance, that is, reduction of internal resistance of the battery is required for the battery for electric vehicles. Further, it is required to extend the life of the battery in order to cope with the long use period of the electric vehicle. The extension of the life as used herein means that not only the battery capacity but also the output decrease is suppressed and the electric energy supply capacity necessary for running the electric vehicle is satisfied for a long period of time.

[0006]

However, in the case of a lithium-ion battery, the lithium deposited by repeated charging reacts with the non-aqueous electrolyte solution each time and forms an irreversible film on the surface of the electrode. The internal resistance increases, the discharge efficiency decreases, and the output and capacity decrease. Moreover, since the output and the capacity are reduced by repeating charging and discharging, the life is shortened, and it is difficult to use such a battery as a power source for an electric vehicle.

In view of the above problems, the present invention can suppress a decrease in capacity and output due to charge / discharge cycles and has a long life, and a non-aqueous electrolyte secondary battery as a power source. It is an object to provide an electric vehicle used in the above.

[0008]

In order to solve the above problems, the first aspect of the present invention uses a carbon material as a positive electrode and a negative electrode active material in which a lithium transition metal composite oxide is used as the positive electrode active material. In a non-aqueous electrolyte secondary battery in which an electrode group having a negative electrode is soaked in a non-aqueous electrolyte and housed in a battery container, the ratio of the internal resistance at a discharge depth of 85% to the internal resistance at a discharge depth of 0%. Is 150% or less.

In this embodiment, the lithium-transition metal composite oxide is used as the positive electrode active material and the carbon material is used as the negative electrode active material to secure a high capacity, high output non-aqueous electrolyte secondary battery. Depth Of Discharge (hereinafter D)
Abbreviated as OD. ) By setting the ratio of the internal resistance at the time of DOD 85% to the internal resistance at the time of 0% (at the time of full charge) to 150% or less, the difference in the internal resistance can be reduced in the entire practical range of charging / discharging. The discharge efficiency can be improved. Therefore, a decrease in output and capacity can be suppressed, and a long-life battery can be obtained.

In this case, the lithium transition metal composite oxide is preferably lithium manganese composite oxide, and the carbon material is more preferably graphitic carbon. At this time, DOD 85% relative to the internal resistance when DOD 0%
The ratio of the internal resistance at that time is preferably 128% or more.

A second aspect of the present invention is an electric vehicle using the non-aqueous electrolyte secondary battery of the first aspect described above as a power source. According to this aspect, since the non-aqueous electrolyte secondary battery in which the decrease in the output and the capacity are suppressed is used as the power source, the acceleration performance and the continuous travel distance are less likely to decrease even if charging and running (discharging) are repeated. Electric vehicles can be realized.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments in which the present invention is applied to a golf cart (electric vehicle) will be described below with reference to the drawings.

As shown in FIG. 1, the golf cart 30 of the present embodiment has a chassis 31 as a base. A battery box 36 accommodating a plurality of cylindrical lithium ion secondary batteries 20 to be described later connected in series is fixed to the chassis 31 at a substantially central portion of the chassis 31. A cushion 35 is arranged on the battery box 36, and the battery box 36 and the cushion 35 form a front seat.

In front of the chassis 31, there is a power transmission mechanism for transmitting the rotational driving force of a motor or a motor shaft using the cylindrical lithium ion secondary battery 20 as a power source to the wheels of the chassis 3.
It is fixed to No. 1 and the power transmission mechanism is structured to rotate the tire. An accelerator pedal 37 for adjusting the forward speed of the golf cart 30 is arranged at the position of the foot of the driver seated in the front seat. The acceleration pedal 37 is connected to a variable resistor that is linked to the amount of depression,
The golf cart 30 has a structure in which the driver depresses the acceleration pedal 37 to move forward according to the amount of depression.

The cylindrical lithium ion battery 20 housed in the battery box 36 is manufactured as follows.

(Production of Positive Electrode Plate) Lithium manganate (LiMn ₂ O ₄ ) powder as a positive electrode active material or lithium cobalt oxide (LiCo) having a specific surface area of 0.55 m ² / g.
O ₂ ) (Nippon Chemical Industry Co., Ltd., trade name Cell Seed)
And graphite powder (produced by Nippon Graphite Industry Co., Ltd., trade name J-SP) and acetylene black (produced by Denki Kagaku Kogyo Co., Ltd., trade name Denka Black) as conductive materials (hereinafter abbreviated as AB). Polyvinylidene fluoride (PVDF) as a binder (binder) is mixed at a predetermined mixing ratio, N-methyl-2-pyrrolidone (NMP) as a dispersion solvent is added thereto, and the kneaded slurry is mixed with a slurry having a thickness of 20 μm. A coating amount of 280 g / m ² was applied to both surfaces of the aluminum foil (positive electrode current collector). At this time, the width of the positive electrode plate is 50 m at one side edge in the longitudinal direction.
The uncoated part of m was left. Then, it was dried, pressed and cut to obtain a positive electrode plate having a width of 139 mm, a predetermined length and a predetermined thickness of the active material mixture application portion. The bulk density of the positive electrode active material mixture layer is 2.
It was set to 65 g / cm ³ . A notch was made in the uncoated portion, and the remaining notch was used as a positive electrode lead piece. Adjacent positive electrode lead pieces are 50 mm apart, and the width of the positive electrode lead pieces is 8 m.
m.

(Production of Negative Electrode Plate) Amorphous carbon powder (produced by Kureha Chemical Industry Co., Ltd., Carbotron) or mesophase spheroidal graphite powder (produced by Kawasaki Steel Co., Ltd.) as an anode active material.
Manufactured by trade name KMFC) and vapor-grown carbon fiber as a conductive material (Showa Denko KK, trade name VGCF) (hereinafter CF
Is abbreviated. ) Or AB, various combinations of PVDF as a binder are mixed at a predetermined mixing ratio, and N of the dispersion solvent is added to the mixture.
The slurry in which MP was added and kneaded was applied to both surfaces of a rolled copper foil (negative electrode current collector) having a thickness of 10 μm in a predetermined application amount. At this time, an uncoated portion having a width of 50 mm was left on one side edge in the lengthwise direction of the negative electrode plate. Then dry, press and cut to a width of 14
A negative electrode plate having a thickness of 5 mm and a predetermined length and a predetermined thickness of the active material coating portion was obtained. The negative electrode plate was compressed so that the porosity of the negative electrode active material mixture layer was about 35%. A notch was made in the uncoated portion similarly to the positive electrode plate, and the remaining notch was used as a negative electrode lead piece. Adjacent negative electrode lead pieces were spaced 50 mm apart, and the width of the negative electrode lead pieces was 8 mm.

(Production of Battery) As shown in FIG. 2, the positive electrode plate and the negative electrode plate produced as described above are wound together with a polyethylene separator having a width of 151 mm and a thickness of 40 μm so as not to come into direct contact with each other. A rolling group (electrode group) 6 was obtained. A hollow cylindrical shaft core 1 made of polypropylene was used as the center of winding. At this time, the positive electrode lead piece 2 and the negative electrode lead piece 3 were positioned on opposite end surfaces of the winding group 6, respectively. In addition, the lengths of the positive electrode plate, the negative electrode plate, and the separator are adjusted so that the diameter of the winding group 6 is 64 ± 0.3 m.
m.

The positive electrode lead piece 2 is deformed, and all of them are
After gathering and contacting with the periphery of the flange portion that integrally projects from the periphery of the positive electrode current collecting ring 4 that is substantially on the extension of the axis 1 of the winding group 6, the positive electrode lead piece 2 and the peripheral surface of the collar portion are contacted. Was ultrasonically welded to connect the positive electrode lead piece 2 to the peripheral surface of the collar portion. On the other hand, the operation of connecting the negative electrode current collecting ring 5 and the negative electrode lead piece 3 was performed in the same manner as the operation of connecting the positive electrode current collecting ring 4 and the positive electrode lead piece 2.

After that, an insulating coating was applied to the entire circumference of the flange portion of the positive electrode current collecting ring 4. For this insulating coating, an adhesive tape was used in which the base material was polyimide, and one surface of which was coated with an adhesive consisting of hexamethacrylate. The adhesive tape was wound over the outer peripheral surface of the winding group 6 from the flange peripheral surface to form an insulating coating, and the winding group 6 was inserted into a nickel-plated steel battery container 7. The outer diameter of the battery container 7 is 67 mm and the inner diameter is 66 mm.

A negative electrode lead plate 8 for electrical conduction is welded to the negative electrode current collecting ring 5 in advance. After the winding group 6 is inserted into the battery container 7, the bottom of the battery container 7 and the negative electrode lead plate 8 are joined together. Welded.

On the other hand, the positive electrode current collector ring 4 is welded with a positive electrode lead 9 which is constructed by stacking a plurality of aluminum ribbons in advance, and the other end of the positive electrode lead 9 is sealed in the battery container 7. Welded to the underside of the battery lid for. The battery lid is provided with a cleaving valve 11 as an internal pressure releasing mechanism that cleaves in response to an increase in the internal pressure of the cylindrical lithium ion battery 20. The cleavage pressure of the cleavage valve 11 was set to about 9 × 10 ⁵ Pa. The battery lid includes a lid case 12 and a lid cap 13.
It is composed of a valve retainer 14 for keeping airtightness, and a cleaving valve 11, which are stacked and assembled by caulking the periphery of the lid case 12.

A predetermined amount of non-aqueous electrolytic solution is injected into the battery container 7, and then the battery container 7 is covered with the battery cover so that the positive electrode lead 9 is folded, and the PFA resin gasket 10 is inserted.
The cylindrical lithium ion battery 20 was completed by caulking and sealing via.

In the non-aqueous electrolyte, 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solution of ethylene carbonate, dimethyl carbonate and diethyl carbonate at a volume ratio of 1: 1: 1. I used one. In addition, the cylindrical lithium-ion battery 20 is electrically operated in accordance with an increase in battery temperature, such as a PTC.
There is no (Positive Temperature Coefficient) element or a current interrupting mechanism that disconnects the electrical lead of the positive electrode or the negative electrode in response to an increase in the internal pressure of the battery.

The cylindrical lithium ion battery 20 is a DOD.
The ratio of the internal resistance at DOD 85% to the internal resistance at 0% was set to 150% or less. The ratio of internal resistance was determined as follows, and it was confirmed that the ratio was 150% or less. After the battery was charged for 4.5 hours under the conditions of constant voltage of 4.2V and limiting current of 30A, the voltage at 10 seconds after discharging at 5A, 15A, 30A and each discharge current was read, and the horizontal axis current value was compared. Is plotted on the vertical axis. The internal resistance when DOD is 0% is calculated from the slope of the approximate straight line connecting the three points.
The internal resistance when adjusted to OD 85% was similarly obtained, and the ratio of the internal resistance at DOD 85% to the internal resistance at DOD 0% was calculated as a percentage. The measurement was performed in an atmosphere with an ambient temperature of 25 ± 1 ° C.

[0026]

EXAMPLES Next, the cylindrical lithium-ion battery 20 and the golf cart 30 manufactured according to this embodiment will be described. Hereinafter, the cylindrical lithium-ion battery 20 will be described in detail in Examples 1 to 4, and the golf cart 30 will be described in detail in Examples 5 to 8. The battery and golf cart of the comparative example prepared for comparison are also shown.

(Example 1 and Example 2) As shown in Table 1 below, in Example 1 and Example 2, lithium cobalt oxide, graphite and AB, and PVDF were mixed in a mass ratio of 85 in the positive electrode plate. : 8: 2: 5 were mixed and used. In Example 1, the negative electrode plate was composed of amorphous carbon powder, CF, and PVD.
F and F were mixed so that the mass ratio was 88: 4: 8, the negative electrode active material coating amount was 102 g / m ² , and the negative electrode material mixture layer bulk density was 0.98 g / cm ^3. Then, the same procedure was performed as in Example 1 except that mesophase spheroidal graphite powder was used as the negative electrode active material, the negative electrode active material coating amount was 146 g / m ² , and the bulk density of the negative electrode mixture layer was 1.40 g / cm ³ . . The ratio of the internal resistance when the DOD was 85% to the internal resistance when the DOD was 0% (hereinafter referred to as the internal resistance ratio; the same in Table 1) was 150% in Example 1 and 133% in Example 2. In Table 1, Co is lithium cobalt oxide, Mn is lithium manganate, and NiC.
o indicates lithium nickel oxide in which a part of nickel in the crystal is replaced with cobalt, amorphous indicates amorphous carbon, and graphite indicates mesophase spheroidal graphite.

[0028]

[Table 1]

Example 3 As shown in Table 1, Example 3
Then, the same procedure was performed as in Example 1 except that lithium manganate was used as the positive electrode active material and the amount of the negative electrode active material applied was 69 g / m ² . The internal resistance ratio was 144%.

Example 4 As shown in Table 1, Example 4
Then, the same procedure was performed as in Example 2 except that lithium manganate was used as the positive electrode active material and the amount of the negative electrode active material applied was 108 g / m ² . The internal resistance ratio was 128%.

(Embodiment 5 to Embodiment 8) In Embodiment 5 to Embodiment 8, 72 cylindrical lithium ion batteries 20 produced in Embodiment 1 to Embodiment 4 are connected in series to the golf cart 30. equipped.

Comparative Example 1 As shown in Table 1, Comparative Example 1
Then, in the positive electrode active material, lithium nickel oxide (LiNiCoO) in which 20% of nickel in the crystal was replaced with cobalt was used.
₂ ) was used and the coating amount of the negative electrode active material was set to 154 g / m ² and the same as in Example 1. The internal resistance ratio was 175%.

Comparative Example 2 As shown in Table 1, Comparative Example 2
Then, the same procedure was performed as in Example 2 except that the same lithium nickel oxide as in Comparative Example 1 was used as the positive electrode active material and the amount of the negative electrode active material applied was 225 g / m ² . The internal resistance ratio was 168%.

Comparative Example 3 In Comparative Example 3, 72 cylindrical lithium ion batteries 20 produced in Comparative Example 1 were connected in series and mounted on a golf cart 30.

<Test / Evaluation> Next, the following series of tests were performed on the batteries and golf carts of the examples and comparative examples produced as described above.

The batteries of Examples and Comparative Examples were charged and then discharged, and the discharge capacity was measured. The charging conditions were a constant voltage of 4.2 V, a limiting current of 30 A, and 4.5 hours. The discharge conditions were a constant current of 10 A and a final voltage of 2.7 V.

After charging under the above conditions, the output was measured. The measurement condition is 5A, 15A, 30A, the voltage at the 10th second at each discharge current is read, plotted on the vertical axis against the horizontal axis current value, and the approximate straight line connecting the three points intersects 2.7V. The product of the current value of V and 2.7 V was used as the output.

Next, each battery was subjected to a cycle test in which the charging / discharging was repeated 100 times under the above-mentioned conditions in an atmosphere of an ambient temperature of 60 ° C., and then the output and the discharge capacity were measured and the initial output and the discharge capacity were compared. The ratio was calculated as a percentage and used as the output retention rate and the discharge capacity retention rate. As a matter of course, the higher the maintenance rate of these, the better the life characteristics.

The above-mentioned discharge capacity and output measurements were carried out in an atmosphere having an ambient temperature of 25 ± 1 ° C.

For the golf cart, constant-speed running was started with the mounted battery at DOD 0%, and the continuous running distance until the golf cart could not maintain the constant speed was measured. Further, the time required for the loaded battery to start with the DOD of 0% and the golf cart reaching a predetermined speed was measured and used as the acceleration time. After removing the battery from the golf cart and performing the above-described cycle test, the battery was mounted on the golf cart again and the continuous running distance and the acceleration time were measured in the same manner. The ratio to the initial continuous running distance and the acceleration time was obtained as a percentage, and the results were used as the continuous running distance maintenance rate and the acceleration time change rate.

The results of the discharge capacity maintenance rate and the output maintenance rate are shown in Table 2 below, and the results of the continuous running distance maintenance rate and the acceleration time change rate are shown in Table 3 below.

[0042]

[Table 2]

As shown in Table 2, in the batteries of Examples 1 to 4, batteries having a high discharge capacity retention rate and a high output retention rate were obtained. On the other hand, in the batteries of Comparative Example 1 and Comparative Example 2, the internal resistance ratio exceeded 150%, and therefore the discharge capacity maintenance ratio and the output maintenance ratio were remarkably low.

In the batteries of Examples 3 and 4 in which lithium manganate was used as the positive electrode active material, in contrast to the batteries of Examples 1 and 2 in which the negative electrodes were the same and lithium cobalt oxide was used as the positive electrode active material. The output retention rate was high. Further, in the batteries of Examples 2 and 4 in which spherical graphite was used as the negative electrode active material, the discharge capacity retention ratio and the output retention ratio were compared with the batteries of Examples 1 and 3 in which amorphous carbon was used. Both showed high values. Among them, in the battery of Example 4 in which lithium manganate was used as the positive electrode active material and spherical graphite was used as the negative electrode active material, and the internal resistance ratio was 128%, both the discharge capacity maintenance ratio and the output maintenance ratio showed the highest values. .

[0045]

[Table 3]

As shown in Table 3, the golf carts of Examples 5 to 8 equipped with the batteries of Examples 1 to 4 were:
Compared to the golf cart of Comparative Example 3 equipped with the battery of Comparative Example 1, both the continuous running distance maintenance rate and the acceleration time change rate were higher. Even after a cycle test equivalent to virtual charging and repeated running, reduction in continuous running distance and acceleration time was suppressed to an extremely low level, resulting in a high-performance golf cart.

Further, from Tables 2 and 3, it was found that the discharge capacity maintenance rate of the battery and the continuous running distance maintenance rate of the golf cart, the output maintenance rate of the battery and the acceleration time change rate of the electric vehicle have a correlation with each other. did.

As is clear from the above examples and comparative examples, the cylindrical lithium ion battery 20 of this embodiment is
Since the ratio of the internal resistance when the DOD is 85% to the internal resistance when the OD is 0% is 150% or less, the difference in the internal resistance can be reduced in the entire practical range of charging and discharging.
The discharge efficiency was improved, the decrease in output and discharge capacity could be suppressed, and a long-life battery could be obtained. In particular, when lithium manganate was used as the positive electrode active material or spherical graphite was used as the negative electrode active material, a battery with a longer life could be obtained. In particular, lithium manganate is used as a positive electrode active material, spherical graphite is used as a negative electrode active material, and D
When the ratio of the internal resistance when the DOD was 85% to the internal resistance when the OD was 0% was 128% or more, a battery having a longer life could be obtained. Golf carts equipped with these batteries have a continuous mileage even after repeated charging and running.
It was possible to make a high-performance golf cart with little reduction in acceleration time.

In this embodiment, the secondary battery used as the power source for the electric vehicle is exemplified, but the size and the battery capacity of the battery are not limited, and the battery capacity is generally 3 to.
It has been confirmed that the present invention remarkably exerts its effect on a battery of about 30 Ah to about 100 Ah. Further, although a cylindrical battery is exemplified in the present embodiment, the present invention is not limited to the shape of the battery, and can be applied to a prismatic battery and other polygonal batteries. Furthermore, the applicable shape of the present invention may be other than the above-mentioned battery having a structure in which the battery upper lid is closed by caulking in the bottomed cylindrical container (can). An example of such a structure is a battery in which the positive and negative external terminals penetrate the battery lid and the positive and negative external terminals are pressed against each other via the shaft core in the battery container. Furthermore, the present invention is also applicable to a non-aqueous electrolyte secondary battery in which the positive electrode and the negative electrode do not have a winding type structure but have a laminated type structure.

Further, in this embodiment, lithium manganate or lithium cobalt oxide was used as the positive electrode active material, but lithium can be inserted / removed as the positive electrode active material for the non-aqueous electrolyte secondary battery of the present invention. And a lithium transition metal complex oxide in which a sufficient amount of lithium is inserted in advance, lithium manganate having a spinel structure, manganese or a part of lithium in the crystal other than them, for example, F
A material substituted or doped with an element such as e, Co, Ni, Cr, A1, Mg or a material in which a part of oxygen in the crystal is substituted or doped with an element such as S or P may be used. . Furthermore, even if a lithium manganese composite oxide capable of a battery voltage of 5 V is used, the effect of the present invention is not changed. In general, lithium manganate can be synthesized by mixing a suitable lithium salt such as lithium carbonate with manganese dioxide such as manganese dioxide and firing the mixture, but by controlling the charging ratio of the lithium salt and manganese oxide. A desired Li / Mn ratio can be obtained.

Further, although amorphous carbon or graphite is used as the negative electrode active material in the present embodiment, the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention is other than the matters described in the above claims. There is no particular limitation. For example, natural graphite, various artificial graphite materials, carbon materials such as coke, etc. may be used, and the particle shape thereof is not particularly limited, and may be scale-like, spherical, fibrous, lump-like or the like.

The conductive material and the binder are not particularly limited in the battery of the present invention, and any of the commonly used materials can be used. Examples of binders (binders) that can be used in other embodiments include Teflon (registered trademark), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, and cyano. There are polymers such as ethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride and chloroprene fluoride, and mixtures thereof.

Furthermore, in this embodiment, the insulating coating is
An example using a pressure-sensitive adhesive tape in which a base material is polyimide and an adhesive composed of hexamethacrylate is applied to one surface thereof, for example, the base material is a polyolefin such as polypropylene or polyethylene, and hexameta A pressure-sensitive adhesive tape coated with an acrylic pressure-sensitive adhesive such as acrylate or butyl acrylate, or a tape made of polyolefin or polyimide not coated with a pressure-sensitive adhesive can also be preferably used.

In this embodiment, 1 mol / liter of lithium hexafluorophosphate is dissolved in a mixed solution of ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1 in the non-aqueous electrolyte. However, the battery of the present invention is not particularly limited, and a general lithium salt is used as an electrolyte, and a nonaqueous electrolytic solution obtained by dissolving this in an organic solvent may be used. For example, as the electrolyte, LiC
_{lO 4, LiAsF 6, LiPF 6} , LiBF 4, Li
_{B (C 6 H 5) 4} , CH 3 SO 3 Li, CF 3 SO 3 L
i or the like or a mixture thereof can be used. As the non-aqueous electrolyte organic solvent, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-
Diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-
Dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitonyl, ethyl methyl carbonate, or the like, or a mixed solvent of two or more of these may be used, and the mixing ratio is not limited.

Furthermore, in the above embodiment, a golf cart using only a cylindrical lithium ion battery as a power source was illustrated, but the present invention is not limited to this, and may be used in combination with an internal combustion engine. Good. Further, the number of batteries to be mounted on the electric vehicle may be appropriately combined depending on the desired output and capacity, and the installation location of the batteries is not particularly limited.

[0056]

As described above, according to the present invention,
By using a lithium transition metal complex oxide as a positive electrode active material and a carbon material as a negative electrode active material, a high capacity, high output non-aqueous electrolyte secondary battery is secured, and DOD 85% relative to the internal resistance at DOD 0%. By setting the ratio of the internal resistance to 150% or less, it is possible to reduce the difference in the internal resistance in the entire range of charging / discharging practically. Therefore, the discharge efficiency is improved and the reduction of the output and the capacity is suppressed. Therefore, it is possible to obtain an effect that a battery having a long life can be obtained.

[Brief description of drawings]

FIG. 1 is a side view schematically showing a golf cart of an embodiment to which the present invention is applicable.

FIG. 2 is a cross-sectional view of a cylindrical lithium ion battery of an embodiment to which the present invention can be applied.

[Explanation of symbols]

6 winding group (electrode group) 7 battery container 20 cylindrical lithium ion battery (non-aqueous electrolyte secondary battery) 30 golf cart (electric vehicle) 35 front seat 36 battery box 37 accelerator pedal

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3D035 AA06 BA01                 5H029 AJ05 AK03 AL07 AM02 HJ16                 5H050 AA07 BA17 CA09 CB08 HA16                 5H115 PA15 PC06 PG07 PI16 PI29                       UI35 UI40

Claims (5)

[Claims] 1. An electrode group having a positive electrode using a lithium transition metal composite oxide as a positive electrode active material and a negative electrode using a carbon material as a negative electrode active material is soaked in a non-aqueous electrolyte and housed in a battery container. In the non-aqueous electrolyte secondary battery described above, the ratio of the internal resistance at a discharge depth of 85% to the internal resistance at a discharge depth of 0% is 150% or less. 2. The lithium transition metal complex oxide is a lithium manganese complex oxide.
The non-aqueous electrolyte secondary battery according to. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the carbon material is graphitic carbon. 4. The non-aqueous electrolyte secondary battery according to claim 3, wherein the ratio is 128% or more. 5. An electric vehicle using the non-aqueous electrolyte secondary battery according to any one of claims 1 to 4 as a power source.