JP3409861B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to a non-aqueous electrolyte secondary battery,
Battery using a porous polyethylene thin film for the separator
It relates to improvement of characteristics. [0002] 2. Description of the Related Art In recent years, portable electronic devices and cords have been developed.
Are rapidly progressing, and these driving power supplies
Small, lightweight, high energy density secondary batteries
High demand. In this respect, non-aqueous secondary batteries, especially lithium batteries
Secondary batteries have high voltage and high energy density
There is great expectation as a battery that does. [0003] When a non-aqueous electrolyte battery is converted to a secondary battery, it is already used.
In the market, nickel-cadmium storage with excellent performance
Due to the existence of batteries (Ni-Cd batteries) and lead-acid batteries,
High energy density is required for the positive electrode active material of non-aqueous electrolyte secondary batteries
That is, a capacitor having a high capacity and a high voltage is desired. this
LiCoO to satisfy the demand_TwoAnd LiMn_TwoO _Four
Materials that exhibit a high voltage of approximately 4V in the system are included. On the other hand, as the negative electrode, metal
Carbon that can store and release lithium alloys and lithium ions
Materials are being considered, but lithium metal can be charged and discharged.
Of short-circuit due to dendrites
However, lithium alloys have problems such as collapse of electrodes due to charging and discharging.
Each of these problems has been
The material is promising as a negative electrode for lithium secondary batteries
You. [0005] SUMMARY OF THE INVENTION A battery using a non-aqueous electrolyte
Batteries, such as lithium secondary batteries, use non-aqueous electrolyte
The degree of conductivity is only about 1/10 of the conductivity of the aqueous electrolyte
Therefore, it is generally difficult to extract current. Non-aqueous electrolyte
The electrode plate of the secondary battery has the same current characteristics as an aqueous secondary battery.
It is made thin and long so that it has a large electrode area.
are doing. In such a case, a problem occurs in security. Non
Since an organic solvent is often used as a solvent for the water electrolyte,
When the pond falls into a short circuit due to some kind of momentum,
The part is heated by Joule heat due to a large short-circuit current,
Solvent flash point reached, causing ignition or even explosion
May be up to. In particular, LiCoO is used as a positive electrode active material._TwoAnd LiMn
_TwoO_FourUsing a material that exhibits a high voltage of about 4 V in the system,
Large potential difference further increases short-circuit current, ensuring safety
Is further reduced. [0007] To solve these problems, 150 ° C
Closes micropores by thermal melting at near temperature to eliminate porosity
And shut off the current (so-called shutdown function
The porous membrane made of polypropylene is used as a separator.
It is often used. But made of this polypropylene
The separator electrolyzes a low-viscosity organic solvent with a low flash point.
When used for liquids, pores are closed by thermal melting of the separator.
The temperature at which the porosity is lost and the current is cut off is too high
Before igniting the organic solvent and igniting,
Cause an explosion. For that reason, recently, materials for separators
Quality is about 110-120 ℃
Yes, even lower polyethylene than polypropylene
There is a tendency to move. However, polyethylene separator
However, the pore size, porosity, and air permeability change
Therefore, there is a danger of ignition or explosion. [0008] The present invention is compared with a conventional non-aqueous electrolyte secondary battery.
In comparison, it maintains a high energy density and ignites during a short circuit,
Excellent safety without explosion, equivalent to current characteristics of conventional batteries
To provide a non-aqueous electrolyte secondary battery having the above performance
With the goal. [0009] [MEANS FOR SOLVING THE PROBLEMS]
The non-aqueous electrolyte secondary battery of the present invention has the general formula Li_1-XMO _Two
(However, M is selected from the group consisting of Co, Ni, Mn, and Fe.
X represents at least one element, wherein X is 0 ≦ X <1
Represents a number. ), A negative electrode made of a carbonaceous material,
A separator impregnated and held with a non-aqueous electrolyte;
The rotator is made of a porous polyethylene membrane and has a thickness of 20 to
30 μm, air permeability according to method A of ASTM D726
200-1000sec / 100cc air, average pore size
0.02 to 0.05 μm. [0010] The air permeability here is based on ASTM D7.
26, membrane area 6.4cm based on method A^Two, Pressure 124m
mH_TwoRequired for 100cc of air in O to pass
It is measured in time (sec). [0011] The non-aqueous electrolyte secondary battery of the present invention has the general formula Li
_1-XMO_Two(However, M is Co, Ni, Mn, Fe
Represents at least one element selected from the group consisting of
≤X <1. ) Consisting of positive electrode, carbonaceous material
Negative electrode and a separator impregnated with non-aqueous electrolyte
The separator is made of a porous polyethylene membrane,
The film thickness is 20 to 30 μm, according to the method A of ASTM D726.
Air permeability is 200 ~ 1000sec / 100cc empty
The average pore size is 0.02 to 0.05 μm.
By using the specific separator of the invention, the unipolar potential
Shows high voltage of 4V as LiCoO_TwoAnd LiMn_TwoO_Foursystem
Material can be used as a positive electrode active material,
Maintains energy density and does not ignite or explode when short circuit occurs
Excellent safety, large discharge capacity and good current characteristics
An excellent non-aqueous electrolyte secondary battery can be provided. [0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.
I will explain. FIG. 1 shows a non-aqueous electrolysis of one embodiment of the present invention.
FIG. 2 is a partial vertical sectional view of a liquid battery secondary battery, for example, having a diameter of 1;
It is a cylindrical battery with a height of 5 mm and a height of 50 mm. In FIG. 1, reference numeral 1 denotes a negative electrode made of a carbonaceous material;
Is a separator, 3 is a positive electrode, and this positive electrode is a gasket.
Connected to rivet 11 caulked to 12 with titanium lead 7
Active material is applied or filled on the titanium positive electrode current collector 5
It is formed. Separator 2 is an organic solvent
For example, diethyl carbonate (hereinafter referred to as D)
EC) and ethylene carbonate (hereinafter referred to as EC)
A mixed solvent having a volume ratio of 1: 1 with an inorganic solvent.
Supporting electrolyte such as LiPF₆Dissolve the thing
Porous polyethylene (hereinafter referred to as PE)
U) consisting of a membrane. The separator 2 is located between the negative electrode 1 and the positive electrode 3.
And the whole is spirally wound to form a group of electrodes
I have. The carbonaceous material of the negative electrode is a nickel-plated iron case.
Nickel negative electrode connected to nickel lead 6 by nickel lead 6
The current collector 4 is coated or filled. This negative electrode 1
The electrode group consisting of the parator 2 and the positive electrode 3 has an upper part
The top insulating plate 8 is applied to the bottom, and the bottom insulating plate 9 is applied to the bottom.
We are inserted in case 10. 12 is polypropylene
Gasket 13 is a cap-shaped terminal that forms the positive terminal.
You. The main component of the positive electrode 3 is a positive electrode mixture.
Is, for example, 100 parts by weight of the positive electrode active material,
A current collector having a composition of black 7 and a fluororesin binder 4
5 so that the filling capacity is 1400 mAh.
You. The mixture mainly composed of carbonaceous material of the negative electrode 1 is also
Filling capacity (at 300 mAh / g carbon utilization)
It is set to be 800 mAh. The above configuration
Using a pond, Li_1-XMO_Two(However, M is
At least one selected from the group consisting of Co, Ni, Mn, and Fe
Each represents one type of element, and X represents a number satisfying 0 ≦ X <1. )
LiCoO which is an example of_TwoUsing the separation of the present invention
FIG. 2 shows the results of a short-circuit test of the battery using the battery. The battery used in the short-circuit test has a charging current of 70 m.
A up to 4.2 V and discharge at 70 mA up to 3.0 V
Charge and discharge after repeated 20 cycles under discharge conditions
Condition. Further, LiCoO is used as a positive electrode active material._Twouse
Then, 1C (700 m) of a battery using the separator of the present invention is used.
The current curve in A) is shown in FIG. Charging condition is 70mA
To 4.2V. Various physical properties of the separator whose characteristics were compared
The values are shown in Table 1. In Table 1, PE is polyethylene,
PP indicates polypropylene. Also, the porosity is separated
Ratio of the area (B) of the hole in the area (A) with
A (%). The air permeability is clear from the definition of the air permeability.
As is clear, the smaller the value of the air permeability, the easier it is to pass gas
No. [0020] [Table 1] FIG. 2 shows various separators shown in Table 1 above.
Among the non-aqueous electrolyte secondary batteries using A, B,
Shows the results of short circuit test for D, F and H
Yes, in FIG. 2, A₁, B₁, D₁, F₁, H₁about
Are No. A, B, D, F, H
Indicates the current value, A_Two, B_Two, D_Two, F_Two, H_Twoabout
Are No. A, B, D, F, H
Indicates the battery outer wall temperature. As can be seen from FIG. 2, a separator made of PP
A and B are polarized when the current cutoff temperature is 150 ° C
Has a point, so the battery temperature is expected to fall
However, the flash point of DEC, which is a low-viscosity solvent, is actually
Temperature and subsequently exploded. P
The behavior using product E separator H is the same as A and B
showed that. This has high permeability as a separator.
Large porosity and short circuit current flow
The flash point of the solvent has been reached due to
It is a thing. From this, the air permeability is 200 sec / 100
If it is not more than cc air, safety in case of short circuit cannot be maintained
I understand. In contrast, the air permeability is 200-60
Separators D and F in the range of 0 sec / 100 cc air
The one used also has a reduced short circuit current and a battery temperature of 110
Explosion without reaching the flash point of solvent
No ignition occurred and the safety was found to be excellent. The permeability is a linear correlation between the porosity and the pore size.
Due to the relationship, if the porosity and pore size increase, the air permeability
Becomes smaller. In addition, the film thickness is less than 20 μm
Full PE separators have low tensile strength and are used in battery plates.
When set on a group machine, the strength is weak and it is cut.
It turned out to be undesirable. Also, PE Separee
If the thickness of the battery exceeds 30 μm, the internal volume of the battery is limited.
Is used to reduce the volume of the electrode plate,
There is a disadvantage that a battery having a high density cannot be obtained, which is not preferable. FIG. C, D, E, F, G
FIG. 4 is a diagram showing a discharge curve at the time of 1C discharge of a nonaqueous electrolyte secondary battery.
is there. In other words, only for polyethylene separators, 1C
It is a discharge curve at the time of performing (700 mA) discharge. As can be seen from FIG. 3, the air permeability is 1000 s.
1200 sec / 100 exceeding ec / 100cc air
G of cc air is 200-600 sec / 100c
c using separators C, D, E and F in the range of air
It was found that the discharge voltage was lower and weaker to high-rate discharge. Further, the discharge voltage increases as the air permeability decreases.
I found out. Air permeability is 200 to 600 sec / 1
Using separators C, D, E, F in the range of 00cc air
The conventional battery has a capacity of 95% or more at the time of 1C discharge.
Showed equivalent or better current characteristics. Although not shown in Table 1, it is used in the present invention.
The permeability of the PE separator was 600 sec / 10
From 0cc air to 1000sec / 100cc air
Showed almost the same good results. As can be seen from the above, the material of the separator and
Is better for polyethylene than for polypropylene.
Use a low-viscosity solvent with a low
When used as, the safety is greatly improved. Also, from the viewpoint of both safety and current characteristics,
Air permeability of 200-1000 sec even with a separator of styrene
c / 100cc air is safe and has excellent current characteristics
I understood that. In addition, the pore size of the micropores of the separator is an average pore size.
0.02 μm or more is necessary for smooth diffusion of ions.
Therefore, it is preferable that the average pore diameter is large from the viewpoint of current characteristics.
However, if the average pore size exceeds 0.05 μm,
Increase the number of minute internal short circuits,
I know it ca n’t be stopped. Here, LiCoO is used as the positive electrode active material._Two
Was used, but Li exhibiting a high voltage was used. _1-XMO_Two(However,
M is at least selected from the group consisting of Ni, Mn and Fe
Also represents one type of element, and X represents a number satisfying 0 ≦ X <1. )
Any lithium transition metal composite oxide can be used. [0033] As is clear from the above description, the present invention
Has higher energy than conventional non-aqueous electrolyte secondary batteries.
Maintains the density and ensures safety without ignition or explosion in the event of a short circuit
Excellent, with performance equal to or better than current characteristics of conventional batteries
A non-aqueous electrolyte secondary battery can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view of a non-aqueous electrolyte secondary battery in one embodiment of the present invention. FIG. 2 is a diagram showing the results of a short-circuit test of non-aqueous electrolyte secondary batteries of one example of the present invention and a comparative example. FIG. 3 is a diagram showing a discharge curve at the time of 1C discharge of the non-aqueous electrolyte secondary batteries according to one embodiment of the present invention and a comparative example. [Description of Signs] 1 negative electrode 2 separator 3 positive electrode 4 negative electrode current collector 5 positive electrode current collector 6 negative electrode lead 7 positive electrode lead 8 upper insulating plate 9 bottom insulating plate 10 case 11 rivet 12 gasket 13 cap-shaped terminal

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Kono 3-1 Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Tonen Chemical Co., Ltd. Technology Development Center (72) Inventor Kotaro Takida Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa No. 3-1 Tonen Chemical Co., Ltd. Technology Development Center (56) References JP-A-3-105585 (JP, A) JP-A-63-121260 (JP, A) JP-A-3-245458 (JP, A) JP-A-63-276868 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 2/16 H01M 10/40

Claims (1)

(57) [Claims] [Claim 1] The general formula Li _1-X MO ₂ (where M is C
X represents at least one element selected from the group consisting of o, Ni, Mn, and Fe, and X represents a number satisfying 0 ≦ X <1. ), A negative electrode made of a carbonaceous material, and a separator impregnated with a non-aqueous electrolyte. The separator is made of a porous polyethylene film, has a thickness of 20 to 30 μm, and has an air permeability (ASTM D726, Method A). 200-1)
000sec / 100cc air, average pore size is 0.02-
A non-aqueous electrolyte secondary battery having a thickness of 0.05 μm.