JP3462722B2 - Polymer electrolyte battery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte battery having a microporous membrane in which pores are filled with a polymer electrolyte provided between a positive electrode and a negative electrode. The present invention relates to a polymer electrolyte battery in which, when the volume of a negative electrode changes, charging / discharging can be sufficiently performed without suppressing this volume change.

[0002]

2. Description of the Related Art Conventionally, an aqueous or non-aqueous electrolytic solution has been generally used as an electrolyte in a battery, but in recent years, a polymer composed of a polymer has been used instead of such a liquid electrolyte. Polymer electrolyte batteries using electrolytes have come to the fore.

That is, in the polymer electrolyte battery using the polymer electrolyte as described above, there is less concern about leakage and corrosion, and the battery structure is simpler than that using the electrolyte solution. There is an advantage that the assembly becomes easy.

Here, in such a polymer electrolyte battery, a polymer electrolyte in which a solute such as a lithium salt is contained in the polymer or an electrolytic solution in which a solvent is added to the lithium salt in the polymer is contained. In addition to the polymer electrolyte provided between the positive electrode and the negative electrode, the polymer electrolyte as described above is filled in the pores of the microporous membrane, and the microporous membrane is placed between the positive electrode and the negative electrode. There was one that was set up in.

Here, in the polymer electrolyte battery in which the pores of the microporous membrane are filled with the polyelectrolyte as described above and the microporous membrane is provided between the positive electrode and the negative electrode, the When the positive electrode and the negative electrode of the volume change, this volume change is suppressed by the microporous membrane filled with the above-mentioned polymer electrolyte, storage of lithium ions and the like to the positive electrode and the negative electrode is not sufficiently performed, this polymer There are problems that the charge and discharge capacity of the electrolyte battery is reduced and the cycle characteristics are deteriorated.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above problems in a polymer electrolyte battery in which a microporous membrane having a polymer electrolyte filled in the pores is provided between a positive electrode and a negative electrode. That is, when the volume of the positive electrode or the negative electrode changes due to charge / discharge, the volume change of the positive electrode or the negative electrode is suppressed by the microporous membrane in which the pores are filled with the polymer electrolyte. Less,
An object of the present invention is to obtain a polymer electrolyte battery having a sufficient charge / discharge capacity and excellent cycle characteristics.

[0007]

Means for Solving the Problems] In the polymer electrolyte battery in claim 1 of the present invention, to solve the above problems, the microporous membrane polymer electrolyte is filled into pores positive In the polymer electrolyte battery provided between the negative electrode and the negative electrode , polyethylene or
Is made of polypropylene and has a porosity of 80% or more.
In addition to the above, the polymer electrolyte was filled in the pores of the microporous membrane in a volume ratio of 20 to 90%.

When filling the pores of the microporous membrane with the polymer electrolyte as in the polymer electrolyte battery according to the first aspect, a microporous membrane having a porosity of 80% or more is used. At the same time, when the pores of the microporous membrane are filled with the polymer electrolyte in a volume ratio of 20 to 90%, the polymer electrolyte is sufficiently filled in the microporous membrane, While sufficient contact with the positive electrode and the negative electrode allows smooth movement of lithium ions and the like, on the other hand, since there are pores not filled with the polymer electrolyte in the above microporous membrane, the positive electrode or Even when the volume of the negative electrode changes, the volume change is less likely to be suppressed by the microporous film, and sufficient charge / discharge capacity is obtained and the cycle characteristics are improved.

Here, as the above-mentioned polymer electrolyte, it is also possible to use a polymer electrolyte in which a solute such as a lithium salt is contained in a polymer, but this polymer electrolyte is contacted with a positive electrode or a negative electrode. In order to improve the mobility and improve the mobility of lithium ions and the like, it is preferable to use a polymer containing an electrolyte solution in which a solute such as a lithium salt is dissolved in a solvent. The ratio of the electrolyte solution to the polymer (electrolyte solution / polymer) is weight in order to obtain the mobility of the polymer and to prevent the electrolyte solution contained in the polymer from reacting with the positive electrode and the negative electrode. The ratio is 0.
It is preferable to use a polymer electrolyte in the range of 1 to 1.9.

As the polymer used in the above-mentioned polymer electrolyte, a polymer which has been generally used in the past can be used, but a volume which can follow the above-mentioned volume change of the positive electrode and the negative electrode. It is preferable to use a polymer having elasticity, for example, a polymer having a polystyrene chain as a main chain and polyethylene oxide as a side chain. When such a polymer is used, the charge / discharge capacity and cycle characteristics of the polymer electrolyte battery are further improved.

Further, as described above, polyethylene or poly
If a microporous membrane composed of propylene is used, this
The porous film has sufficient strength, and even if the film thickness is reduced,
Does not break due to the volume change of the negative electrode,
And the like, and the charge and discharge capacity is further improved.
It is also chemically stable and suppresses reaction with electrolytes.
Will be controlled.

Here, in the above polymer electrolyte battery, when lithium ions are used as an active material, as a positive electrode material used for the positive electrode, a well-known positive electrode material which has been generally used in the past should be used. For example, a lithium-transition metal composite oxide containing at least one of manganese, cobalt, nickel, iron and vanadium can be used.

As the negative electrode material constituting the negative electrode, for example, metallic lithium, lithium alloys, carbon materials capable of inserting and extracting lithium ions, carbon materials such as coke, organic material fired bodies, SnO ₂ , SnO, TiO _{2 are} used. ₂ , Nb ₂
A metal oxide or the like having a lower potential such as O ₃ than the positive electrode material can be used.

In the above-mentioned polymer electrolyte, examples of the lithium salt contained in the polymer include lithium trifluoromethanesulfonate, lithium trifluoromethanesulfonate imide, lithium trifluoromethanesulfonate methide and lithium hexafluorophosphate. ,
Lithium hexafluoroarsenate, lithium tetrafluoroborate and the like can be used.

When the electrolyte solution containing the lithium salt dissolved in a solvent is contained in the polymer, the solvent may be, for example, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, cyclopentanone, Sulfolane, dimethylsulfolane, 3-methyl-1,3-oxazolidine-2-
ON, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, butyl methyl carbonate,
Solvents such as ethylpropyl carbonate, butylethyl carbonate, dipropyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate are used alone or in combination of two or more. be able to.

[0016]

EXAMPLES Hereinafter, the polymer electrolyte battery according to the present invention will be specifically described with reference to experimental examples. In the case of the polymer electrolyte battery satisfying the conditions of the present invention, the polymer electrolytes not satisfying the conditions of the present invention will be described. It is clarified that the charge and discharge capacity and cycle characteristics are improved compared to batteries. In addition,
The polymer electrolyte battery according to the present invention is not limited to those shown in the following experimental examples, and can be implemented by appropriately changing it without departing from the scope of the invention.

(Experimental Examples 1 to 10) In these experimental examples, as shown in FIG. 1, a microporous membrane 3 having pores filled with a polymer electrolyte was provided between a positive electrode 1 and a negative electrode 2. Then, a flat coin-shaped polymer electrolyte battery was manufactured.

[Preparation of Positive Electrode] In preparing the positive electrode 1, lithium-containing cobalt dioxide LiCo was used as a positive electrode material.
Using O ₂ powder, this LiCoO ₂ powder, carbon powder that is a conductive agent, and a solution of polyvinylidene fluoride powder that is a binder dissolved in N-methyl-2-pyrrolidone (NMP) are mixed. , A LiCoO ₂ powder, a carbon powder, and a polyvinylidene fluoride powder in a weight ratio of 85: 10: 5 were prepared, and this slurry was prepared from one surface of a positive electrode current collector 5 made of ferritic stainless steel and having a thickness of 20 μm. It is applied to the surface by the doctor blade method and dried at 150 ° C. to form a disc with a diameter of 10 mm and a thickness of about 80 μm.
A positive electrode 1 having

[Preparation of Negative Electrode] In preparing the negative electrode, graphite powder was used as a negative electrode material, and the graphite powder was mixed with a solution of polyvinylidene fluoride powder as a binder in NMP to obtain graphite powder. And a polyvinylidene fluoride powder in a weight ratio of 95: 5 were prepared, and this slurry was made to have a thickness of 20 made of ferritic stainless steel.
A negative electrode current collector 6 having a thickness of 10 μm was coated on one surface by a doctor blade method, and dried at 150 ° C. to prepare a negative electrode 2 having a disk shape with a diameter of 10 mm and a thickness of about 60 μm.

[Preparation of Microporous Membrane Filling Porosity with Polymer Electrolyte] Here, the microporous membrane 3 is made of polypropylene having a porosity of 90% and a thickness of 30 μm. While using a microporous membrane, as the polymer in the polymer electrolyte, one having a polystyrene chain as the main chain and polyethylene oxide in the side chain is used, and the electrolyte to be contained in this polymer includes ethylene carbonate and dimethyl carbonate. LiClO ₄ lithium perchlorate as a mixed solvent of
Was used at a ratio of 1 mol / l.

Then, a solution is prepared by dissolving the above-mentioned polymer having a polystyrene chain as the main chain and polyethylene oxide in the side chain in various concentrations in diethyl carbonate as a solvent to prepare the above-mentioned microporous membrane 3 as described above. 1 for each solution
After immersing for 20 minutes to impregnate the pores of each microporous membrane 3 with each of the above solutions, each microporous membrane 3 is allowed to stand on the above positive electrode 1, and The solvent in each was evaporated to fill the pores of each microporous membrane 3 with the above polymer.

Then, the above-mentioned electrolytic solution is added to the polymer filled in the pores of each of the microporous membranes 3 in a weight ratio of 1: 1 to form a gel polymer electrolyte. I chose Then, the volume ratio (filling ratio) of the gelled polymer electrolyte in the pores of each microporous membrane 3 was determined, and the results are shown in Table 1 below.

[Preparation of Battery] Next, a polymer electrolyte battery is prepared by using the positive electrode 1 prepared as described above, the negative electrode 2, and each microporous membrane 3 having pores filled with the polymer electrolyte. In producing the above, the above negative electrode 2 is overlaid on each microporous film 3 formed on the positive electrode 1 as described above, and the microporous film 3 is sandwiched between the positive electrode 1 and the negative electrode 2. Then, this is housed in a battery case 4 formed of a positive electrode can 4 a and a negative electrode can 4 b, and a positive electrode 1 is provided via a positive electrode current collector 5.
Is connected to the positive electrode can 4a while the negative electrode 2 is connected to the negative electrode can 4b through the negative electrode current collector 6, and the positive electrode can 4a and the negative electrode can 4b are electrically insulated by the insulating packing 7.
The polymer electrolyte batteries of Experimental Examples 1 to 10 in the form of coins were manufactured.

Next, each of the above polymer electrolyte batteries was charged at a charging current density of 100 μA / 25 ° C. under the condition of 25 ° C.
After charging with cm ² until the charging end voltage 4.2 V, discharge current density 100 .mu.A / cm ² in discharged to a discharge end voltage of 2.75 V, which repeatedly performed by the charge and discharge as 1 cycle, 1 cycle and 200 cycles In the eyes
The discharge capacity (mAh / cm ² ) per 1 cm ² of the positive electrode in each polymer electrolyte battery was determined, and the results are shown in Table 1 below.
It is also shown.

[0025]

[Table 1]

As is clear from these results, the microporous membrane 3
In each of the polymer electrolyte batteries of Experimental Examples 2 to 9, in which the filling rate of the polymer electrolyte filled in the pores with respect to the pores was in the range of 20% to 90% satisfying the condition of the present invention,
Compared with the polymer electrolyte batteries of Experimental Examples 1 and 10 which do not satisfy the conditions of the present invention, the discharge capacity is large and the cycle deterioration of the capacity is small. In particular, the filling rate is 20%.
In the polymer electrolyte batteries of Experimental Examples 2 to 6 in which the range was up to 60%, the discharge capacity was further increased and the cycle characteristics were also improved.

(Experimental Examples 11 to 20) In Experimental Examples 11 to 20, in [Preparation of Microporous Membrane in which Pores are Filled with Polymer Electrolyte] in Experimental Examples 1 to 10 above, polypropylene In filling the polymer in the microporous membrane 3 of 1., polyvinylidene fluoride is used as the polymer, and solutions prepared by dissolving the polyvinylidene fluoride in NMP at various concentrations are prepared. 3 was immersed in each of the above-mentioned solutions for 120 minutes to fill the pores of each microporous membrane 3 with polyvinylidene fluoride, and otherwise, in the same manner as in the case of Experimental Examples 1 to 10 above. Then, each polymer electrolyte battery was produced.

Also, regarding each of the polymer electrolyte batteries of Experimental Examples 11 to 20, in the same manner as in the above-described Experimental Examples 1 to 10, in each of the polymer electrolyte batteries in the first cycle and the 200th cycle. The discharge capacity (mAh / cm ² ) per 1 cm ^{2 of the} positive electrode was determined, and the results are also shown in Table 2 below.

[0029]

[Table 2]

As a result, also in Experimental Examples 11 to 20, as in the case of Experimental Examples 1 to 10 described above, the microporous membrane 3 was used.
In each of the polymer electrolyte batteries of Experimental Examples 12 to 19 in which the filling rate of the polymer electrolyte filled in the pores to the pores was in the range of 20% to 90% satisfying the conditions of the present invention, Compared with the polymer electrolyte batteries of Experimental Examples 11 and 20 which do not satisfy the conditions of the invention, the discharge capacity is large and the cycle deterioration of the capacity is small, and in particular, the filling rate is in the range of 20% to 60%. In the polymer electrolyte batteries of Experimental Examples 12 to 16, the discharge capacity was further increased and the cycle characteristics were also improved.

(Experimental Examples 21 to 30) In Experimental Examples 21 to 30, in the above-mentioned Experimental Examples 1 to 10 [Preparation of Microporous Membrane Filled with Polymer Electrolyte in Pores] In filling the polymer into the microporous membrane 3 of 1., polyethylene oxide was used as the polymer, and solutions prepared by dissolving the polyethylene oxide in acetonitrile as solvent at various concentrations were prepared. Each of the above solutions was immersed for 120 minutes so that the pores of each microporous membrane 3 were filled with polyvinylidene fluoride, and other than that, in the same manner as in the case of Experimental Examples 1 to 10 above, Each polymer electrolyte battery was produced.

Also, regarding each of the polymer electrolyte batteries of Experimental Examples 21 to 30, in the same manner as in the above Experimental Examples 1 to 10, in the first cycle and the 200th cycle,
The discharge capacity (mAh / cm ² ) per positive electrode 1 cm ² in each polymer electrolyte battery was determined, and the results are shown in Table 3 below.
It is also shown.

[0033]

[Table 3]

As a result, also in Experimental Examples 21 to 30, as in the case of Experimental Examples 1 to 10 described above, the microporous membrane 3 was used.
In the polymer electrolyte batteries of Experimental Examples 22 to 29 in which the filling rate of the polymer electrolyte filled in the pores of the above with respect to the pores was in the range of 20% to 90% satisfying the conditions of the present invention, Compared with the polymer electrolyte batteries of Experimental Examples 21 and 30, which do not satisfy the conditions of the invention, the discharge capacity is large and the cycle deterioration of the capacity is small. In particular, the filling rate is in the range of 20% to 60%. In the polymer electrolyte batteries of Experimental Examples 22 to 26, the discharge capacity was further increased and the cycle characteristics were also improved.

Further, the above Experimental Examples 1 to 10 and Experimental Example 11
˜20 and each of the polymer electrolyte batteries of Experimental Examples 21 to 30 are compared, the polymer in the polymer electrolyte filled in the pores of the microporous membrane 3 has a polystyrene chain as a main chain and polyethylene oxide as a side chain. The polymer electrolyte batteries of Experimental Examples 1 to 10 using the polymer having the above have a larger discharge capacity than the polymer electrolyte batteries of Experimental Examples 11 to 20 and Experimental Examples 21 to 30 using other polymers. Also, the cycle deterioration of the capacity was reduced, and it was preferable to use, as the polymer in the polymer electrolyte, a polymer having a polystyrene chain as a main chain and polyethylene oxide as a side chain.

(Experimental Examples 31 to 41) In Experimental Examples 31 to 41,
In addition, [Polymer Electrolysis in Experimental Examples 1 to 10 above]
In the production of a microporous membrane in which the quality is filled in the pores]
For the polymer in the molecular electrolyte, the
The same polystyrene chain as the main chain and polyethylene on the side chain
A polymer containing oxide is used, and this polymer is
The microporous membrane 3 made of polypropylene was filled in the pores.
Afterwards, the polymer filled in this way contains the above electrolyte solution
In doing so, the weight ratio of the electrolytic solution to the polymer (electrolysis
Liquid / polymer) was adjusted as shown in Table 4 below.
Polymer electrolytes containing gel electrolyte containing gel
However, as in the case of Experimental Example 5 described above,
Each polymer electrolyte is filled with 50% filling rate.
A degradable battery was produced.

Also, regarding each of the polymer electrolyte batteries of Experimental Examples 31 to 40, in the same manner as in the above-mentioned Experimental Examples 1 to 10, in each of the polymer electrolyte batteries in the first cycle and the 200th cycle. The discharge capacity (mAh / cm ² ) per 1 cm ^{2 of the} positive electrode was determined, and the results are also shown in Table 4 below.

[0038]

[Table 4]

As a result, when the electrolyte filled in the polymer filled in the pores of the microporous membrane 3, the weight ratio of the electrolyte to the polymer (electrolyte / polymer) is 0.1 to 1. 9
In each of the polymer electrolyte batteries of Experimental Examples 5 and 33 to 37 in which the range of 5 was satisfied, the discharge capacity was large and the cycle deterioration of the capacity was small.

(Experimental Examples 41 to 43) In Experimental Examples 41 to 43, the polymer electrolyte was used in [Preparation of Microporous Membrane with Porous Electrolytes Filled] in Experimental Examples 1 to 10 above. By changing the type of microporous membrane 3 to be filled,
As shown in Table 5 below, in Experimental Example 41, the film thickness was 30 μm.
m is a polyethylene microporous membrane having a porosity of 90%, Experimental Example 42 is a polypropylene nonwoven fabric having a film thickness of 90 μm and a porosity of 90%, and Experimental Example 43 is a film having a thickness of 80 μm and a porosity of 85%. Each of the polymer electrolyte batteries was produced in the same manner as in Experimental Example 5 except that the polyvinylidene fluoride was used.

Also, regarding each of the polymer electrolyte batteries of Experimental Examples 41 to 43, in the same manner as in the above Experimental Examples 1 to 10, in each of the polymer electrolyte batteries in the first cycle and the 200th cycle. The discharge capacity (mAh / cm ² ) per 1 cm ^{2 of the} positive electrode was determined, and the results are also shown in Table 5 below.

[0042]

[Table 5]

As a result, in the case of each polymer electrolyte battery of Experimental Examples 5 and 41 in which the polypropylene microporous membrane or the polyethylene microporous membrane was used as the microporous membrane 3 for filling the polymer electrolyte, these microporous membranes 3 were used. Although it was possible to reduce the thickness and increase the discharge capacity, in the polymer electrolyte batteries of Experimental Examples 42 and 43 using polypropylene non-woven fabric and polyvinylidene fluoride, the strength of polypropylene non-woven fabric and polyvinylidene fluoride was higher. Since it is weak, the film thickness must be increased, and the discharge capacity is greatly reduced as compared with those in Experimental Examples 5 and 41. In Experimental Example 43 using polyvinylidene fluoride, the electrolytic solution is The cycle characteristics were also deteriorated by the reaction with.

[0044]

As described above in detail, in the polymer electrolyte battery according to the first aspect of the present invention, the microporous membrane having the pores filled with the polymer electrolyte is provided between the positive electrode and the negative electrode. In filling the polymer electrolyte into the pores of the microporous membrane, a microporous membrane having a porosity of 80% or more is used, and the pores of the microporous membrane are filled with the polymer electrolyte. 20% to 90% by volume of polymer electrolyte
Since the polymer electrolyte is sufficiently filled with the positive electrode and the negative electrode, the movement of lithium ions and the like can be performed smoothly while the pores of the microporous membrane not filled with the polymer electrolyte are filled. Even when there is a portion and the positive electrode and the negative electrode change in volume due to charge and discharge, this change in volume is less likely to be suppressed by the microporous membrane, and sufficient charge and discharge capacity can be obtained, and cycle characteristics can be improved. Also improved. Further, the polymer according to claim 1
In an electrolyte battery, the above-mentioned microporous membrane has a polypropylene
Made to use a microporous membrane of ren or polyethylene
Therefore, even if the film thickness is reduced, it may be
Does not break and is chemically stable and reacts with electrolytes, etc.
Polymer electrolyte without deterioration of cycle characteristics
The charge / discharge capacity of the battery was further improved.

As described in claim 2 of the present invention,
When a polymer electrolyte containing an electrolytic solution in a polymer is used and the ratio of the electrolytic solution to the polymer (electrolyte / polymer) is in the range of 0.1 to 1.9 by weight, The contact property between the polymer electrolyte and the positive electrode or the negative electrode is improved, and the electrolytic solution contained in the polymer does not react with the positive electrode or the negative electrode, and the charge / discharge capacity and cycle characteristics in the polymer electrolyte battery are improved. Further improved.

Further, as described in claim 3 of the present invention,
When a polymer having a polystyrene chain as a main chain and polyethylene oxide as a side chain is used as the polymer in the polymer electrolyte, the polymer is deformed following the volume change of the positive electrode or the negative electrode, and The charge / discharge capacity and cycle characteristics were further improved.

[0047]

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view showing the internal structure of a polymer electrolyte battery produced in an experimental example.

[Explanation of symbols]

1 positive electrode 2 Negative electrode 3 Microporous membrane

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Noma 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Koji Nishio, 2-5 Keihan Hondori, Moriguchi City, Osaka Prefecture No. 5 within Sanyo Electric Co., Ltd. (56) Reference JP-A-10-247521 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/40 H01M 2/16

Claims (3)

(57) [Claims] 1. A polymer electrolyte battery thus provided between the microporous membrane polymer electrolyte is filled into pores positive and negative, as the microporous film of the polyethylene also
Is made of polypropylene and has a porosity of 80% or more.
With use of those Tsu, an empty hole of the microporous membrane, a polymer electrolyte battery, characterized in that said polymer electrolyte is filled in a range of 20% to 90% by volume. 2. The polymer electrolyte battery according to claim 1, wherein a polymer electrolyte in which an electrolyte solution is contained in a polymer is used, and a weight ratio of the electrolyte solution to the polymer in the polymer electrolyte is 0.1. The polymer electrolyte battery is in the range of ˜1.9. 3. The polymer electrolyte battery according to claim 1 or 2, wherein the polymer in the polymer electrolyte is
A polymer electrolyte battery comprising a polymer having a polystyrene chain as a main chain and polyethylene oxide as a side chain.