JP3433695B2 - Cylindrical lithium-ion battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a cylindrical lithium ion
In particular, the positive electrode, the negative electrode, and the cell
An electrode winding group in which a parator is wound and each electrode from the electrode winding group.
A connection part for connecting to a terminal and an electrolyte are built-in,
When the internal pressure of the battery container reaches a predetermined value, the internal pressure is reduced.
Internal pressure reduction mechanism, battery capacity is 3Ah or more and output
It relates to a cylindrical lithium ion battery of 400 W or more. [0002] 2. Description of the Related Art A lithium ion secondary battery has a high energy
-By taking advantage of the density,
For powering portable devices such as notebook computers and mobile phones
It is used. Inside a cylindrical lithium ion secondary battery
The active material is applied to the metal foil for both the positive and negative electrodes.
These two electrodes are sandwiched by a separator.
The cross section is spirally wound so as not to contact directly, and the winding group
Are formed in a wound structure. And this
The winding group is housed in a cylindrical battery can serving as a battery container,
After the electrolyte is injected, it is sealed. A typical cylindrical lithium ion secondary battery has
Outer dimensions are 18650 type, diameter 18mm,
With a height of 65 mm, it can be used with small consumer lithium-ion batteries.
It is widely spread. 18650 type lithium ion two
The positive electrode active material of secondary batteries is characterized by high capacity and long life
Lithium cobaltate is mainly used for battery capacity.
The amount is about 1.3Ah to 1.7Ah, and the output is about
It is about 10W. On the other hand, the automobile industry is facing environmental problems
Completely battery-free power source with no emissions
Development of electric vehicles and the connection between internal combustion engine and batteries
Development of hybrid (electric) vehicles using both power sources
Has been accelerated and has reached a practical stage. Electric car
Of course, the rechargeable battery, which is the power source for
A secondary battery that satisfies these requirements, requiring the characteristics to be obtained
Lithium-ion batteries are attracting attention. [0005] SUMMARY OF THE INVENTION
In the case of mu-ion batteries, the higher the output, the more safety
It tends to be emphasized, especially for power supplies for electric vehicles.
This is especially true for high-capacity, high-power batteries
It is. In addition, high capacity and high output batteries are
Current charging and large current discharging
As is generally the case with lithium ion batteries,
A current cutoff mechanism that operates in response to a constant increase in battery internal pressure.
Type of disconnect switch in the battery structure is difficult
No. [0006] In the case of an electric vehicle that runs on a person, a charging system is required.
When overcharging when the control system is broken,
Battery crashes that you might encounter in the event of a collision
Battery, when piercing a foreign object, external short circuit, etc.
Ensuring body safety is the minimum and very important
These are important battery characteristics. Battery safety here means that
The behavior of the battery when the pond is exposed to abnormal conditions
Naturally, no damage to the vehicle
This means minimizing damage. In view of the above proposal, the present invention has a high capacity and a high output.
Yet extremely safe cylindrical lithium ion
It aims to provide an on-battery. [0008] [MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
In addition, the present invention provides a positive electrode, a negative electrode and a separator in a cylindrical battery container.
Electrode-wound group in which the electrodes are wound, and from the electrode-wound group to each electrode terminal
A connection part for connection and an electrolyte are built-in,
When the internal pressure of the vessel reaches a predetermined value, the internal pressure is reduced.
With a reduction mechanism, battery capacity is 3Ah or more and output 400
In the cylindrical lithium ion battery of W or more,
To the positive electrode active material mixture containing lithium manganese double oxide
Negative electrode active material, wherein the negative electrode contains amorphous carbon
The mixture is applied and the solvent of the electrolyte is ethylene
-Bonate,Dimethyl carbonate and diethyl carbonate
NeToMixed solventTherefore, the volume ratio of each solvent is
30% or more eachYes,SaidThe solute of the electrolyte is
Lithium phosphate (LiPF₆)After the solute dissolution
The concentration of the electrolyte is 0.7 mol / L to 0.8 mol / L
literIt is characterized by being. According to the present invention, a high capacity, high output cylindrical
Lithium is used for the positive electrode to secure
Positive electrode active material mixture containing manganese double oxide
A negative electrode active material mixture containing amorphous carbon is applied to the negative electrode.
Have been. The cylindrical lithium-ion battery
Large current charge or large current discharge when exposed to normal conditions
The state is maintained and the electrolyte and the mixture of the positive and negative electrode active materials
Generates gas by chemical reaction and raises internal pressure of cylindrical battery container
May be caused. Generally, cylindrical lithium ion batteries
In order to prevent the internal pressure of this cylindrical battery container from rising,
For example, a safety valve that releases gas at a predetermined internal pressure to the outside of a container or a crack
Although it has an internal pressure reduction mechanism such as a valve,
Tylene carbonate,Dimethyl carbonate and diethyl
LucerbonayToMixed solventIs the volume of each solvent
30% or more for each ratioAnd the solute of the electrolyte is hexafluorinated
Lithium phosphate,The concentration of the electrolyte after dissolution of the solute is set to 0.
7 mol / l to 0.8 mol / lTo do
Gas is rapidly released from the internal pressure reduction mechanism
It takes place very calmly withoutHigh capacity, high output
However,It can be a battery with excellent safety
You. [0010] [0011] DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Referring to the drawings, FIG.
Of a cylindrical lithium ion battery to which the present invention is applied
One embodiment will be described. <Production of Electrode Plate> As shown in FIG.
The cylindrical lithium ion battery 20 according to the embodiment has a positive electrode current collector.
A belt-like positive electrode having a positive electrode active material layer W2 formed on both surfaces of a body W1.
A negative electrode active material layer W4 is formed on both sides of the electrode and the negative electrode current collector W3
Cut through the strip-shaped negative electrode and the strip-shaped separator W5.
It has a winding group W wound in a plane spiral. The positive electrode current collector W1 is made of aluminum having a thickness of 20 μm.
Um foil. The positive electrode active material layer W2 is made of a lithium active material.
Composite oxide, graphite as a conductive additive, and Vine
Polyvinylidene fluoride (PVDF) and electrolyte
And is a constituent material. The negative electrode current collector W3 has a thickness of 10
μm copper foil. The negative electrode active material layer W4 is made of lithium ion
Lithium ions are used as electrode reactive species,
The carbon material of the negative electrode active material, which absorbs and releases, and the binder
Consists of polyvinylidene fluoride (PVDF) and electrolyte
Substance. To form the positive electrode active material layer W2, the positive electrode active material layer W2 is formed.
Lithium manganate as substance (average particle size about 20μm)
Or lithium cobaltate (average particle size about 20 μm),
Fight (average particle size about 5μm) and PVDF in weight ratio
Mix them so that each becomes 80:10:10, then go there
N-methyl-2-pyrrolidone (NMP) as a dispersion solvent
Add an appropriate amount, knead and disperse thoroughly, and form a slurry.
You. This kneaded material is transferred from roll to roll (roll
By two-roll transfer) on both surfaces of the positive electrode current collector W1
After applying evenly and uniformly to the same thickness and drying,
The electrode thickness is compressed to a predetermined thickness by pressing
The material layer W2 is obtained. However, at this stage,
Not. On the other hand, to form the negative electrode active material layer W4,
Amorphous carbon or graphite and PVDF as negative electrode active material
Mix so that the weight ratio is 90:10,
Add an appropriate amount of NMP as a dispersing solvent to the
To form a slurry. This kneaded material is roll-to-
Is substantially uniform on both sides of negative electrode current collector W3 by roll transfer
After coating and drying to the same thickness, press
The thickness of the negative electrode active material layer W
Get 4. However, do not include electrolyte at this stage.
No. In the present embodiment, Kureha Chemical Co., Ltd.
Trade name: CARBOTRON P (average particle size: 20μ)
m) and natural graphite (average particle size 10 μm) as graphite
Was used. <Preparation of Battery>
40μm thick microporous polyethylene between the pole and anode
Wound so that the separator W5 made of a film is arranged.
Turned into a wound group W, positive electrode current collecting rings at both ends of the wound group W
10, the negative current collecting ring 11 is arranged,
, Each current collector was welded. Positive current collecting ring 10, negative electrode
The current collecting ring 11 has a positive current collecting ring support 8 and a negative electrode
Fixed to the end of the winding core 17 via the current collecting ring support 9
is there. This winding group W with a current collecting ring is
Insert the battery into the battery can 16 so that the 11 side is the bottom of the can.
Negative electrode lead previously welded to negative electrode current collector ring 11
The plate 14 is welded to the battery can 16. At this time, the negative electrode current collector
The winding group W is fixed between the ring 11 and the battery can 16.
The negative electrode current collecting ring spacer 7 is disposed. Also, the positive electrode
The positive electrode lead plate B13 is previously melted on the upper surface of the current collecting ring 10.
Keep in touch. On the other hand, an upper lid cap 1, an upper lid case 2,
An upper lid composed of all valves 3 and valve retainers 4 is separately manufactured,
The positive electrode lead plate A12 is welded to the upper lid case 2 by welding.
Install it. A winding group W is provided on the upper edge of the positive electrode current collection ring 10.
A positive current collecting ring spacer 6 for fixing
You. Freedom of positive lead plate A12 and positive lead plate B13
The ends are welded to connect the top lid and the winding group W with current collecting ring.
Continue. In this state, 50 ml of the electrolyte is poured into the battery can 16.
Enter. Then, the upper lid is put through the insulating gasket 5.
High output by placing and caulking on top of battery can 16
Type cylindrical lithium ion battery 20 is assembled
You. <Example> Next, the cylindrical lithium ion
The details of the embodiment of the battery 20 will be described. Also book
Comparative example manufactured at the same time so that the effect of the example becomes clear
The battery is also described.BookExample 2 according to the embodiment
See Table 1 for the batteries of the following examples and comparative examples.
The description of the same parts as in the first embodiment will be omitted,
Only parts will be described.Examples 2 to 4 and Example 6,
The battery of No. 7 is also shown for reference, and the battery of the present invention
Out of range. (Embodiment 1) As shown in Table 1, this embodiment
Uses lithium manganate as the positive electrode active material,
The thickness of the material layer W2 is 98 + -2 μm, and the density is 2.6.
5g / cm³And Using amorphous carbon as the negative electrode active material,
The thickness of the negative electrode active material layer W4 is 60 + -2 μm, and the density is
About 1.02g / cm³And Electrolyte is ethylene carbonate
30% by volume of nate, 35% by volume of dimethyl carbonate,
In a mixed solvent of 35% by volume of diethyl carbonate,
Lithium hexafluorophosphate (LiPF₆) To 0.8
1 / liter dissolved. [0021] [Table 1](Embodiment 2) In this embodiment, mixing of an electrolytic solution
Solvent was 30% by volume ethylene carbonate, dimethyl carbonate
The material used was made 70% by volume of boronate. (Embodiment 3) In this embodiment, the solvent mixture of the electrolytic solution is
30% by volume of carbonate, 70% of diethyl carbonate
The volume% was used. Example 4 In this example, LiP was used as a solute in the electrolyte.
F₆Was dissolved in 0.6 mol / liter. Embodiment 5 In this embodiment, LiP is used as a solute in the electrolyte.
F₆Was dissolved in 0.7 mol / liter. (Embodiment 6) In this embodiment, LiP is used as a solute in the electrolytic solution.
F₆Was dissolved at 1.3 mol / l. (Embodiment 7) In this embodiment, LiP was used as a solute in the electrolytic solution.
F₆Was dissolved at 1.4 mol / l. (Comparative Example 1) In this comparative example, cobalt oxide
The thickness of the negative electrode active material layer W4 is 90 + -2 μm using
m was used. Comparative Example 2 In this comparative example, the thickness of the positive electrode active material layer W2 was
110 + -2 μm, using graphite as negative electrode active material, density
About 1.4 g / cm³Was used. Comparative Example 3 In this comparative example, LiC was used as a solute in the electrolytic solution.
10₄Was used. Comparative Example 4 In this comparative example, LiB was used as a solute in the electrolytic solution.
F₄Was used. (Second Embodiment) Next, the present invention is applied.
Second Embodiment of Cylindrical Lithium-ion Battery
explain. <Preparation of Electrode Plate> As shown in FIG.
The cylindrical lithium ion battery 120 according to the embodiment has a rated capacity.
A high-capacity battery with a capacity of 50 Ah or more
In the same manner as in the first embodiment, the positive electrode
A strip-shaped positive electrode on which the active material layer W2 is formed, and a negative electrode current collector W
3, a strip-shaped negative electrode in which a negative electrode active material layer W4 is formed on both surfaces.
And a cross-section spirally wound through a belt-shaped separator W5.
The winding group W 'is provided. In addition, the positive electrode current collector W1
Thickness, constituent material and manufacturing method of positive electrode active material layer W2, negative electrode
The thickness of the current collector W3, the constituent materials of the negative electrode active material layer W4, and
The manufacturing method and the material and thickness of the separator W5 are the first actual
It is the same as the embodiment. <Preparation of Battery>
And a 40 μm thick poly so that they do not come into direct contact.
It is wound around an ethylene separator. At this time, the positive electrode
Lead piece 109 of the negative electrode and lead piece 109 of the negative electrode
So that they are located on opposite end faces of the wound group W '.
I do. As shown in FIG.
And the entire lead piece 109 is deformed, and all of the
The pole (alternately to the positive terminal 101) which is almost on the extension of the axis.
Gather around the periphery of the flange 107, which protrudes integrally from the surrounding area.
Contact. Put the lead piece 109 around the periphery of the flange 107
After contact, the lead piece 109 and the peripheral surface of the flange 107
By ultrasonic welding to connect the lead piece 109 to the peripheral surface of the flange 107.
Continue and fix. The negative electrode terminal 101 'and the negative electrode
The connection operation with the lead piece 109 is also performed outside the positive electrode described above.
Part terminal 101 and lead piece 109 derived from the positive electrode
The connection operation is performed in the same manner. Thereafter, the positive external terminal 101 and the negative external terminal
An insulation coating 108 is provided on the entire periphery of the flange 107 of the terminal 101 '.
Apply. This insulating coating 108 is provided on the entire outer peripheral surface of the winding group W '.
Also exert. The base material of the insulating coating 108 is polyimide,
Hexamethacrylate adhesive is applied on one side
A cloth-coated adhesive tape was used. Apply this adhesive tape to the collar 10
Wound multiple layers from the 7th circumference to the outer circumference of the winding group W '
The edge coating 108 is used. The largest diameter part of the winding group W 'is insulated
The number of turns is adjusted to be 108 existing parts, and the maximum diameter is
Wound group W 'slightly smaller than the inner diameter of battery container 105
Into the battery container 105. Next, the back surface of the battery 104 made of alumina
Contact part thickness 2mm, inner diameter 16mm, outer diameter 25mm
The second ceramic washer 103 'is shown in FIG.
The pole is the pole that constitutes the positive electrode external terminal 101, and the tip is
Fit into the poles that make up the negative external terminal 101 '
No. Also, the first ceramic washer 103 is attached to the battery cover 1.
04, the positive external terminal 101 and the negative external terminal 10
1 'each pass through the first ceramic washer 103.
You. Then, the peripheral end surface of the disc-shaped battery lid 104 is
Laser welding of the entire area of both contact parts.
You. At this time, the positive external terminal 101 and the negative external terminal 10
1 ′ penetrates a hole in the center of the battery
104 project outside. And as shown in FIG.
Made of alumina, 2mm thick, 16mm inside diameter, 28mm outside diameter
Flat first ceramic washer 103, nut 10
2 Place a metal washer 111 smoother than the bottom
Fit to the pole external terminal 101 and the negative electrode external terminal 101 '
Inset. The battery cover 104 opens in response to an increase in the internal pressure of the battery.
A rupture valve 110 is provided for rupture. In addition, cleavage valve 1
The breaking pressure of 10 is 13-18 kg / cm²And Next, a metal nut 102 is connected to the positive electrode outer end.
Terminal 101 and the negative external terminal 101 ′.
The second ceramic washer 103 'and the first ceramic washer 103'.
Battery cover 10 via washer 103 and metal washer 111
4 between the flange 107 and the nut 102 to secure it.
You. The tightening torque value at this time is 70 kgf · cm.
did. Keep the metal washer until the tightening operation is completed.
111 did not rotate. In this state, the battery cover 104
Made of rubber (EPDM) interposed between the back surface and the flange 107
Power generation inside the battery container 105 by compression of the O-ring 112
The element is isolated from the outside air. Thereafter, the liquid inlet 11 provided in the battery lid 104
3 to pour 0.33 liter of electrolyte into battery container 105
And then sealing the injection port
The Mion battery 120 was completed. In addition, cylindrical
The internal pressure of the battery container 105 rises in the
The current interrupt mechanism that operates to interrupt the current in response to
Not provided. <Example> (Example 8) Next, a circle manufactured according to the second embodiment will be described.
Regarding the details of Embodiment 8 of the cylindrical lithium ion battery 120,
Will be explained. In the battery of Example 8, as shown in Table 1.
In addition, using lithium manganate as the positive electrode active material, the positive electrode active material
The thickness of the porous layer W2 is 210 + -2 μm, and the density is 2.6.
5g / cm³And Using amorphous carbon as the negative electrode active material,
The thickness of the negative electrode active material layer W4 was set to 130 + -2 μm,
1.02 g / cm³And Electrolyte is ethylene carbonate
30% by volume of nate, 35% by volume of dimethyl carbonate,
In a mixed solvent of 35% by volume of diethyl carbonate,
And LiPF₆0.8mol / liter dissolved
Was used. <Test / Evaluation> [Test] Next, Examples 1 to 8 and
Each battery of Comparative Examples 1 to 4 can be discharged for about 1 hour
4.2V constant voltage at current value (1C), charging time 5 hours, 2
The battery was charged at 5 + -2 ° C. and was fully charged.
3 were performed. (Test 1) A fully charged battery is set at 1 / 2C.
Discharge at current, final voltage 2.5V, 25 + -2 ° C, discharge
The capacitance was checked. This was defined as the rated capacity. (Test 2) Fully charged batteries were charged at 10 A, 30 A, 90
A for 10 seconds each, and charge the battery voltage at 5 seconds.
Point where the straight line plotted against the flow value crosses 2.7V
Output (W) = Ia × 2.7 from the current value (Ia)
I did. (Test 3) Continuous charging at a constant current of 1 C at room temperature, and observe the situation.
Was. In order to quantify the phenomenon, weigh the battery before and after the test.
And the weight after the test was expressed as a percentage. [Test Results] The test results of Test 1 and Test 2 were
Table 2 shows the test results of Test 3 in Table 3. [0036] [Table 2] [0037] [Table 3][Evaluation] As a result of Tests 1 and 2, the battery produced
Has high capacity and high output of more than 3Ah and more than 400W
Have been. The batteries of Examples 1 to 7 showed that
After opening all valves, only smoke or gentle outgassing
Only, there is no deformation of the battery, and the battery weight is more than 80%.
And the safety was ensured. Also, increase battery capacity
No spark was generated even with the battery of Example 8 which was crisp,
Only 80% or more of the battery weight ensures safety.
Was kept. Among them, the battery of Example 1 was heavy before the test.
It retained about the same weight as the quantity. The batteries of Examples 2 and 3 were ethylene carbonate
Example 1 was less than 30% by volume of each solvent except
The weight of the battery was lower than that of the battery. Battery of Example 3
As for, the output also decreased by 10%. The battery of Example 4 is L
iPF₆The concentration is 0.6 mol / l,
The battery of Example 5 was LiPF ₆
Since the concentration is 0.7 mol / liter,
The decrease in power is small. The battery of Example 7 was LiPF₆
The concentration was 1.4 mol / l, and the battery weight after the test was
It is slightly smaller. In this regard, the battery of Example 6 is Li
PF₆Since the concentration was 1.3 mol / liter,
The degree of reduction in battery weight is smaller than that of the battery of Example 7. On the other hand, the batteries of Comparative Examples 1 to 3
A flower has emerged. In the battery of Comparative Example 1, the battery cover came off and sparks
Erupted, and the battery weight decreased. The battery of Comparative Example 2 is safe
Sparks erupted from the valve, and the battery weight was also low. battery
The bottom of the can has swollen considerably. The batteries of Comparative Examples 3 and 4
A little spark came out of the safety valve. Battery can bottom slightly expanded
Was. Therefore, the embodiment1, 5, 8Each battery is high
Despite the capacity and high output, the battery is exposed to abnormal conditions.
Behavior is extremely gentle in the event of
It can be said that it is a pond. Thus, high capacity, high output,
Batteries are particularly suitable for powering electric vehicles
ing. In the above embodiment, the current interruption mechanism
Example of cylindrical lithium-ion battery without
However, the present invention is limited by the presence or absence of a current interruption mechanism
Not something. Even batteries with a current interruption mechanism
When the battery is exposed to abnormal conditions, as
It is assumed that the current is not interrupted by the interrupt mechanism
Therefore, by applying the present invention, the safety of the battery is further improved.
Can be up. In the above embodiment, polyvinyl fluoride is used.
Liden was used as a binder.
The electrode active material binder for
Ron, polyethylene, polystyrene, polybutadiene,
Butyl rubber, nitrile rubber, styrene / butadiene
System, polysulfide rubber, nitrocellulose, cyanoethyl cell
Loin, various latex, acrylonitrile, vinyl fluoride
Nyl, vinylidene fluoride, propylene fluoride, fluoride fluoride
Using polymers such as loloprene and their mixtures
Is also good. Further, the present invention is not limited to the embodiments described above.
Lithium is inserted as the positive electrode active material for
・ It is a detachable material, and a sufficient amount of lithium is inserted in advance.
Lithium manganese compound oxide is preferable, and spinel
Lithium manganate with a structure and manganese in crystals
Or doping of lithium or part of lithium with other elements
The material may be used. [0046] As described above, according to the present invention,
The positive electrode, negative electrode and separator were wound around a cylindrical battery container
To connect the electrode winding group and each electrode terminal from the electrode winding group
And the electrolyte is built-in, and the internal pressure of the battery
Equipped with an internal pressure reduction mechanism that reduces the internal pressure when a certain value is reached.
And a cylinder with a battery capacity of 3 Ah or more and an output of 400 W or more
In a lithium ion battery,
Positive electrode active material mixture containing manganese double oxide
A negative electrode active material mixture containing amorphous carbon is applied to the negative electrode.
And the solvent of the electrolytic solution is ethylene carbonate.
G,Dimethyl carbonate and diethyl carbonateTo
Mixed solventTherefore, the volume ratio of each solvent is 30
%AboveYes,SaidThe electrolyte solute is lithium hexafluorophosphate
Um (LiPF₆)Of the electrolyte solution after dissolution of the solute
The concentration is 0.7 mol / L to 0.8 mol / L
By doing so, the battery is high capacity and high output, but
Extremely mild behavior when exposed to abnormal conditions,
Obtaining a cylindrical lithium-ion battery with excellent safety
it can.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a cylindrical lithium ion battery according to a first embodiment to which the present invention is applied. FIG. 2 is a sectional view of a cylindrical lithium ion battery according to a second embodiment to which the present invention is applied. [Description of Signs] 3 Safety valve 16 Battery can (battery container) 20, 120 Cylindrical lithium ion battery 105 Battery container 110 Cleavage valve W, W 'Wound group (electrode wound group) W1 Aluminum foil (positive electrode current collector) W2 Positive electrode active material layer W3 Copper foil (negative electrode current collector) W4 Negative electrode active material layer W5 Separator

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kensuke Hironaka 2-8-7 Nihonbashi Honcho, Chuo-ku, Tokyo Inside Shin-Kobe Electric Co., Ltd. (56) References JP-A-7-335254 (JP, A) JP-A Heihei JP-A-5-283104 (JP, A) JP-A-2000-260469 (JP, A) JP-A-11-224693 (JP, A) JP-A-2000-67923 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 10/40 H01M 4/00-4/04 H01M 4/36-4/62

Claims (1)

(57) [Claims 1] An electrode winding group in which a positive electrode, a negative electrode, and a separator are wound around a cylindrical battery container, and a connecting portion for connecting the electrode winding group to each electrode terminal. And an internal pressure reducing mechanism for reducing the internal pressure of the battery container when the internal pressure of the battery container reaches a predetermined value.
In a cylindrical lithium ion battery of 0 W or more, a positive electrode active material mixture containing lithium manganese double oxide is applied to the positive electrode, and a negative electrode active material mixture containing amorphous carbon is applied to the negative electrode. , the solvent of the electrolytic solution of ethylene carbonate, the volume ratio of the respective solvent I mixed solvent der containing dimethyl carbonate and diethyl car <br/> Bone bets is its
Respectively not less than 30%, after the solute of the electrolyte the solute dissolved What lithium hexafluorophosphate (LiPF ₆₎ der
The concentration of the electrolyte solution is 0.7 mol / L to 0.8 mol
/ Liter / liter .