JP3262647B2 - Method for producing positive electrode active material for polymer solid electrolyte lithium 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 method for producing a positive electrode active material for a solid polymer electrolyte lithium battery.

[0002]

_2. Description of the Related Art A positive electrode active material layer made of a positive electrode active material such as MnO ₂ , V ₂ O ₅ .nH ₂ O, and a negative electrode active material layer made of metallic lithium are laminated via a polymer solid electrolyte layer. Polymer solid electrolyte lithium batteries having a modified structure are known. In this type of battery, if the positive electrode active material layer contains a lithium-containing positive electrode active material (discharge product) in which metal lithium as a negative electrode active material is previously contained in the positive electrode active material layer before discharging the battery for the first time, It has been known that the charge / discharge cycle characteristics of the battery can be improved. Therefore, conventionally, various methods for including a lithium-containing positive electrode active material in which metal lithium is compounded in a positive electrode active material layer have been studied. Among the above-mentioned positive electrode active material materials, in the case of oxides of transition metals such as MnO ₂ , when mixed with a lithium salt and subjected to chemical synthesis by heating at a high temperature, these oxides are thermally decomposed and LiMnO 2 _Two
Thus, the lithium-containing positive electrode active material can be easily obtained.

[0003]

However, vanadium pentoxide xerogel (V ₂ O ₅ .nH ₂ O) is converted to Li
When such a chemical synthesis method is used to generate a lithium-containing positive electrode active material represented by xV ₂ O ₅ .nH ₂ O, V ₂ O ₅ .nH ₂ O is crystallized by heating.
V ₂ O ₅ .nH ₂ O cannot be combined with Li,
LixV ₂ O ₅ .nH ₂ O cannot be obtained. Further, the amorphous five vanadium oxide (V ₂ O ₅₎ aqueous solution of t- butyllithium in a, was added lithium salt such as lithium hydroxide, dissolved this dried to vanadium pentoxide xerogel (V ₂ O ₅ NH ₂ O) was considered, but an aqueous solution of amorphous vanadium pentoxide (V ₂ O ₅ ) gelled, and thus LixV ₂ O ₅ was also used in such a method.
-NH ₂ O could not be obtained. In addition, LixV
_{Since 2} O ₅ .nH ₂ O is a discharge product, it can be over-discharged before using the battery for the first time so that the lithium-containing positive electrode active material can be contained in the positive electrode active material layer. However, simply over-discharging the battery causes the entire positive electrode active material layer to have a lithium-containing positive electrode active material (L) having an X value within a predetermined range.
ixV ₂ O ₅ .nH ₂ O) cannot be substantially uniformly dispersed, and the charge / discharge cycle characteristics of the battery cannot be sufficiently improved.

An object of the present invention is to provide a cathode active material for a polymer solid electrolyte lithium battery which can be used to form a cathode active material layer containing LixV ₂ O ₅ .nH ₂ O having an X value within a predetermined range. An object of the present invention is to provide a method for producing a substance.

[0005]

The invention of claim 1 is directed to a method for producing a positive electrode active material for a solid polymer electrolyte lithium battery. In the present invention, first, a solution in which a polymer solid electrolyte is dissolved in a solvent and a vanadium pentoxide xerogel powder are provided with an agitating member inside, and placed in an electrolytic tank in which metallic lithium is arranged on the anode, and the agitating member is operated. Electrolysis is performed to produce an electrolytic slurry containing lithium-containing vanadium pentoxide xerogel represented by LixV ₂ O ₅ .nH ₂ O. Then, the solvent is volatilized and removed from the electrolytic slurry taken out of the electrolytic cell to produce a positive electrode active material for a polymer solid electrolyte lithium battery. Incidentally, the solution in which the polymer solid electrolyte is dissolved in the solvent and the vanadium pentoxide xerogel powder may be put in an electrolytic cell in a state of a mixed slurry in which both are mixed,
Both may be put separately in the electrolytic cell.

In the invention of claim 2, LixV ₂ O ₅ .n
Electrolysis is performed in an electrolytic cell so that the value of x of H ₂ O is 0.05 <x <3.0. The value of x can be easily changed by adjusting the amount of electricity when performing electrolysis.

According to the third aspect of the present invention, the stirring member is a cathode.

[0008] The invention of claim 4 is directed to a method for producing a positive electrode active material for a polymer solid electrolyte lithium battery. In the present invention, first, a vanadium pentoxide xerogel film is pulverized to prepare a vanadium pentoxide xerogel powder, and further, a lithium salt is dissolved in a solution in which a polyphosphazene derivative is dissolved in a solvent to form a lithium ion conductive polymer solid electrolyte solution. make. Next, a mixed slurry is prepared by mixing the vanadium pentoxide xerogel powder, the lithium ion conductive polymer solid electrolyte solution and the conductive additive. Next, a stirring member is provided inside, the mixed slurry is put in an electrolytic cell in which the stirring member is used as a cathode, and metal lithium is placed in the anode, and electrolysis is performed while the stirring member is operated to perform electrolytic slurry containing lithium-containing vanadium pentoxide xerogel. make. Next, a material obtained by volatilizing and removing the solvent from the electrolytic slurry taken out of the electrolytic cell is rolled into a sheet by a roller press to form a positive electrode active material sheet, and a positive electrode for a polymer solid electrolyte lithium battery having a predetermined shape is formed from the positive electrode active material sheet. Manufacture active material.

[0009]

According to the first aspect of the present invention, LixV ₂ O is converted from vanadium pentoxide xerogel (V ₂ O ₅ .nH ₂ O) by electrolysis.
_This is a method for producing a lithium-containing positive electrode active material represented by ₅ · nH ₂ O. In the present invention, a mixture of a vanadium pentoxide xerogel powder and a solution obtained by dissolving a polymer solid electrolyte in a solvent is used as an electrolyte for electrolysis, using a polymer solid electrolyte as an electrolyte for electrolysis, whereby LixV ₂ O ₅・ NH ₂
A lithium-containing positive electrode active material represented by O can be easily produced. Moreover, according to the present invention, the vanadium pentoxide xerogel powder in the mixture is electrolyzed while the mixture is being stirred, so that the lithium-containing positive electrode active material (LixV ₂ O) having an X value within a predetermined range in the entire positive electrode active material layer. ₅ · nH ₂ O) can be substantially uniformly dispersed.

In the electrolysis for producing the electrolytic slurry, the value of x of LixV ₂ O ₅ .nH ₂ O is 0.05
It is preferable to carry out such that <x <3.0. When a positive electrode active material containing LixV ₂ O ₅ .nH ₂ O having a value of x of 0.05 or less is used in a battery that does not require initial charge and a metal lithium (negative electrode active material) layer is disposed on the negative electrode side, discharge occurs. There is a problem that the capacity retention rate of the capacity (the ratio of the discharge capacity after the second cycle to the first discharge capacity) decreases. The reason for this is not clear, but for a battery containing a lithium-containing positive electrode active material (LixV ₂ O ₅ .nH ₂ O) in the positive electrode active material layer, the value of x becomes 0.05 or less even after charging. This is because the battery cannot be charged until it becomes. Further, when the value of x is 3.0 or more, there is a problem that it is difficult for the positive electrode active material to return to the charge product.

When the stirring member is configured as a cathode as in the third aspect of the present invention, the apparatus of the battery case for performing electrolysis can be simplified and the electrolysis efficiency (coulomb efficiency) can be increased.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a manufacturing method of an embodiment of the present invention. First, a vanadium pentoxide xerogel powder was prepared as follows. First, an aqueous solution containing 3% by weight of amorphous vanadium pentoxide is applied to a substrate such as a stainless steel plate or an ethylene tetrafluoride resin plate, and then dried to form a vanadium pentoxide xerogel (V ₂ O ₅ .nH ₂ O) film. did. The value of n of V ₂ O ₅ .nH ₂ O is 0.1 <n
It is preferable to form V ₂ O ₅ .nH ₂ O so as to fall within the range of <1.6. When the value of n is 0.1 or less, there is a problem that vanadium pentoxide is easily crystallized. When the value of n is 1.6 or more, the negative electrode active material (lithium)
Reacts with excess bound water, which causes a problem that battery performance is reduced. Next, this vanadium pentoxide xerogel film after grinding peeled from the substrate, 120 ℃, 10 ^-2
Drying under reduced pressure at atmospheric pressure for 16 hours gave a vanadium pentoxide xerogel powder having an average particle size of 10 μm.

Next, methoxy oligoethylene oxy polyphosphazene (MEP), which is a kind of polyphosphazene derivative, and 8% by weight of LiClO _{4 based on the} MEP.
And 1,2-dimethoxyethane (D
ME) was dissolved in a solvent of 13% by weight to prepare a solution for a lithium ion conductive polymer solid electrolyte. In addition, ME
The amount of LiClO ₄ with respect to P is preferably 3 to 18% by weight, and the ratio of dissolving a mixture of MEP and LiClO ₄ in DME is preferably 5 to 20% by weight.

Next, the above-mentioned vanadium pentoxide xerogel powder, a solution for a solid polymer electrolyte, and acetylene black (A
A mixed slurry was prepared by mixing the conductive assistant composed of B) in a weight ratio of 5: 3: 2. The acetylene black used was dried under reduced pressure at 150 ° C. and 10 ⁻² atm for 48 hours. Then, the mixed slurry is put into the electrolytic cell shown in the schematic sectional view of FIG. 1, and the mixed slurry S is stirred while vanadium pentoxide xerogel (V ₂ O ₅ .n
The H ₂ O) powder was converted into a lithium-containing vanadium oxide xerogel (LixV ₂ O ₅ .nH ₂ O) according to the following reaction formula to prepare an electrolytic slurry containing the lithium-containing vanadium pentoxide xerogel. V ₂ O ₅ .nH ₂ O + xLi ⁺ + xe ⁻ → LixV ₂ O
₅ · nH ₂ O Here, the structure of the electrolytic cell shown in FIG. 1 will be described.
In this figure, 1 is an electrolytic container, 2 is an anode, 3 is an anode-side electrolytic member, 4 is a separator, 5 is a stirring member constituting a cathode, 6 is a power source, 7 Denotes a lid for an electrolytic container. The electrolytic vessel 1 is formed of glass and has a cylindrical shape with a diameter of 50 mm and a height of 50 mm. The anode 2 has a structure in which a terminal 2b is connected to a mesh 2a made of stainless steel. The mesh portion 2a has a cylindrical shape, and faces the inner wall surface 1a of the electrolytic container 1 at a predetermined interval. The terminal 2 b is supported by the lid 7, and its end is connected to the positive output terminal of the power supply 6. The anode electrolytic member 3 is made of 500 g of metallic lithium, and is pressed against the entire inner wall 2 c of the mesh 2 a of the anode 2. The separator 4 is formed of a nonwoven fabric made of polypropylene, and divides the inside of the electrolytic container 1 into an anode region 1b and a cathode region 1c. The anode region 1b is filled with a solution Y for a lithium ion conductive polymer solid electrolyte having the same components as those used in preparing the above-mentioned electrolytic slurry.
The mixed slurry S is filled in c. The side surface 4a of the separator 4 on the positive electrode region 1b side is joined to the anode-side electrolytic member 3 and supported by the anode-side electrolytic member 3. The stirring member 5 has a structure in which four stirring blades 5b are connected to the rotating shaft 5a at equal angular intervals. The rotating shaft 5a is formed of a stainless steel tube, and one end is connected to a negative output terminal of the power source 6. The rotating shaft 5a is rotatably supported by the electrolytic container lid 7 via a bearing (not shown) via a bearing (not shown), and is rotationally driven by a motor (not shown). The stirring blade 5b is configured by attaching a stainless steel net to a stainless steel frame fixed to the rotating shaft 5a. The mesh shape and size of the mesh are determined so that the mixed slurry S in the negative electrode region 1c can be stirred uniformly. The electrolytic container lid 7 is formed of glass similarly to the electrolytic container 1.

In this embodiment, the amount of the vanadium pentoxide xerogel powder in the mixed slurry S is set to 5 g, and the rotating shaft 5a
While rotating at 20 r / m, the electrolytic current was set to 10 mA, the cut voltage was set to 2.5 V, and the current was supplied until the electrolytic current reached the cut voltage. Electrolysis was performed until the coulomb amount of the coulometer provided in the external circuit reached 2650 coulombs. When electrolysis is performed until the coulomb amount becomes 2650 coulombs, Li
The average value of x of xV ₂ O ₅ .nH ₂ O is 1.0.

Next, after taking out the electrolytic slurry from the electrolytic bath, the electrolytic slurry was left in an atmosphere of 40 ° C. for 24 hours to volatilize and remove the solvent (DME) from the electrolytic slurry.
Then, the electrolytic slurry from which the solvent was removed by volatilization was rolled into a sheet by a roller press to form a positive electrode active material sheet,
This positive electrode active material sheet has a thickness of 1.18 mm × 35 mm × 35.
By cutting into a size of mm, a positive electrode active material for a polymer solid electrolyte lithium battery having a predetermined shape was completed. The positive electrode active material contained lithium-containing vanadium pentoxide xerogel (LixV ₂
O ₅ .nH ₂ O) was 0.1 g.

Next, using the positive electrode active material produced by the method of this embodiment, a flat polymer solid electrolyte lithium battery having a cross section as shown in FIG. 2 is produced as follows. The life characteristics were examined. First, thickness 20μm
Surface 11 of positive electrode current collector 11 made of nickel foil
The positive electrode active material produced by the method of this example was attached to the central portion of a to form a positive electrode active material layer 12 of vanadium pentoxide xerogel (V ₂ O ₅ .nH ₂ O) having a thickness of 1.18 mm.

Next, a lithium carrier layer (negative electrode active material carrier layer) 13 was formed as follows. First, the lithium ion conductive polymer solid electrolyte used in producing the natural graphite and the above-described positive electrode active material so that the weight ratio of the natural graphite to methoxy oligoethyleneoxy polyphosphazene (MEP) is 3: 7. And the solution for mixing. Then, this was left in an atmosphere of 40 ° C. for 24 hours to evaporate and remove the solvent (DME) to prepare a negative electrode active material holding material. Next, the negative electrode active material holding material was rolled into a sheet by a roller press to form a negative electrode active material holding sheet, and the negative electrode active material holding sheet was formed to a thickness of 0.1%.
By cutting into dimensions of mm × 35 mm × 35 mm, a negative electrode active material holder having a predetermined shape was completed. Then, a negative electrode active material holder was attached to the center of one surface 14a of the negative electrode current collector 14 made of a stainless steel foil having a thickness of 20 μm to form a negative electrode active material holder layer 13 having a thickness of 0.1 mm.

Next, the hot melt 15 is placed on the outer peripheral end 11 b of the positive electrode current collector 11, and the lithium ion conductive material 12 is placed on the positive electrode active material layer 12 so as to entirely cover the positive electrode active material layer 12. The solution for conductive polymer solid electrolyte was applied. Then, the solution for a lithium ion conductive polymer solid electrolyte was dried. Further, a solution for a lithium ion conductive polymer solid electrolyte was applied also on the negative electrode active material holding layer 13, and then the solution for a lithium ion conductive polymer solid electrolyte was dried. Then, the positive electrode current collector 11 and the negative electrode current collector 14 were stacked such that the positive electrode active material layer 12 and the negative electrode active material holding layer 13 faced each other. When the layers are laminated in this manner, the solution for the lithium ion conductive polymer solid electrolyte in a dry state applied to both layers is joined between the positive electrode active material layer 12 and the negative electrode active material holding layer 13 to have a thickness of 100 μm. Is formed. Next, the hot melt 15 is heated so that the outer peripheral ends 11b and 1 of the current collectors 11 and 14 are removed.
4b to complete a solid polymer electrolyte lithium battery. As described above, the positive electrode active material layer of the polymer solid electrolyte lithium battery in which the lithium holder doped with lithium ions (negative electrode active material holder) is disposed on the negative electrode side contains lithium vanadium pentoxide xerogel (LixV ₂ O ₅ .nH).
_When composed of 2O), it is not necessary to dispose the negative electrode active material in the negative electrode active material holder, and the production of the battery is simplified.

Next, the battery was subjected to an electrolytic current of 0.5 mA, a cut voltage of 2.5 V, and a current was supplied until the electrolytic current reached the cut voltage. The battery was repeatedly charged and discharged, and the charge and discharge cycle characteristics of the battery were examined. The charging and discharging were performed under the following conditions. Discharge: 0.5 mA, final voltage: 2.0 V (25 ° C.) Charge: 0.5 mA, final voltage: 4.0 V (25 ° C.)
FIG. 3 shows the measurement results of the charge / discharge cycle characteristics. From this figure, it can be seen that a battery capable of maintaining a relatively high battery capacity of 13 mAh can be obtained by using the positive electrode active material manufactured by the method of the present embodiment even after 200 cycles.

Next, batteries A using two kinds of positive electrode active materials,
B was manufactured, and the initial discharge capacity retention rate (the ratio of the discharge capacity in each cycle to the discharge capacity of the initial discharge) for the charge / discharge cycle of each battery was examined. The positive electrode active material of the battery A is a positive electrode active material manufactured by the method of another embodiment of the present invention, and electrolysis is performed until the average value of x of LixV ₂ O ₅ .nH ₂ O becomes 0.1. Was manufactured in the same manner as in the above-mentioned example. The positive electrode active material of Battery B was V ₂ O ₅ .nH ₂
The positive electrode active material does not contain Li and is represented by O. The batteries A and B each contained 25 mg instead of the negative electrode active material holding layer.
The negative electrode active material layer is formed of metallic lithium, and has the same structure as that of the battery shown in FIG. 2 except for the negative electrode active material holding layer and the positive electrode active material layer. And batteries A and B
The charge and discharge under the same conditions as the charge and discharge cycle characteristics test shown in FIG. 3 were repeated, and the initial discharge capacity retention rate of each battery with respect to the charge and discharge cycles was measured. FIG. 4 shows the measurement results. From this figure, it can be seen that the battery A using the positive electrode active material manufactured by the method of another embodiment of the present invention has a high initial discharge capacity retention ratio (approximately 100) even after 40 charge / discharge cycles.
%), The battery B using the positive electrode active material containing no Li has a low initial discharge capacity retention (about 90%).
%). This is because in the battery A, Li taken in the positive electrode active material in the first discharge is completely desorbed in the next first charge, so that the capacity of the second discharge can be kept high, whereas Li In the battery B using the positive electrode active material containing no Li, the Li taken in the positive electrode active material in the first discharge is charged even when the battery is charged in the next first charge.
This is because 10% of the remaining in the positive electrode active material decreases the capacity of the second discharge by 10%.

In this embodiment, the stirring member is constituted by the cathode, but the present invention is not limited to this, and the stirring member and the cathode may be constituted separately.

[0023]

According to the first aspect of the present invention, Lix is converted from vanadium pentoxide xerogel (V ₂ O ₅ .nH ₂ O) by electrolysis.
This is a method for producing a lithium-containing positive electrode active material represented by V ₂ O ₅ .nH ₂ O. In the present invention, by using the polymer solid electrolyte in the mixed slurry as an electrolyte for electrolysis, by applying a current treatment to a mixture of a vanadium pentoxide xerogel powder and a solution obtained by dissolving the polymer solid electrolyte in a solvent. A lithium-containing positive electrode active material represented by LixV ₂ O ₅ .nH ₂ O can be easily produced. In addition, according to the present invention, the vanadium pentoxide xerogel powder in the mixture is electrolyzed while stirring the mixture, so that the lithium-containing positive electrode active material (Li) having the X value within a predetermined range in the entire positive electrode active material layer.
xV ₂ O ₅ .nH ₂ O) can be substantially uniformly dispersed.

According to the second aspect of the present invention, when used in a battery that does not require initial charging, in which a metal lithium (negative electrode active material) layer is disposed on the negative electrode side, the capacity retention ratio of discharge capacity (2. Thus, the problem that the positive electrode active material is hardly returned to the charge product can be solved.

According to the third aspect of the present invention, since the stirring member is configured as a cathode, the device of the battery case for performing electrolysis can be simplified, and the electrolysis efficiency (coulomb efficiency) can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an electrolytic cell used in a production method of the present embodiment.

FIG. 2 is a cross-sectional view of a battery using the positive electrode active material manufactured by the method of the present example.

FIG. 3 is a diagram showing charge / discharge cycle characteristics of a battery using the positive electrode active material manufactured by the method of the present example.

FIG. 4 is a diagram showing an initial discharge capacity retention ratio for a charge / discharge cycle of a battery used in a test.

[Explanation of symbols]

 2 Anode 3 Anode-side electrolytic member (metal lithium) 5 Cathode (stirring member)

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hayakawa et al. ▲ KU ▼ Beauty 2-1-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside Shin-Kobe Electric Co., Ltd. (72) Inventor Akio Komaki Nishi-Shinjuku, Shinjuku-ku, Tokyo Chome 1-1 Shin Shin Kobe Electric Co., Ltd. 463 Kagasuno, Tokushima Research Laboratories, Otsuka Chemical Co., Ltd. (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01M 4/36-4/62 H01M 4/02-4/04 H01M 10/40

Claims (4)

(57) [Claims] 1. A solution prepared by dissolving a solid polymer electrolyte in a solvent and a vanadium pentoxide xerogel powder are placed in an electrolytic tank provided with a stirring member inside and lithium metal disposed on an anode, and the stirring member is operated. While performing electrolysis, L
An electrolytic slurry containing lithium-containing vanadium pentoxide xerogel represented by ixV2O5.nH2O is prepared, and the solvent is volatilized and removed from the electrolytic slurry taken out of the electrolytic cell to produce a positive electrode active material for a polymer solid electrolyte lithium battery. A method for producing a positive electrode active material for a polymer solid electrolyte lithium battery. 2. The said x of said LixV2O5.nH2O.
The method for producing a positive electrode active material for a polymer solid electrolyte lithium battery according to claim 1, wherein the electrolysis is performed in the electrolytic cell so that the value of A is 0.05 <x <3.0. 3. The method according to claim 1, wherein the stirring member is a cathode. 4. A vanadium pentoxide xerogel film is pulverized to form a vanadium pentoxide xerogel powder, and a lithium salt is dissolved in a solution in which a polyphosphazene derivative is dissolved in a solvent to form a lithium ion conductive polymer solid electrolyte solution. Making a mixed slurry by mixing the vanadium pentoxide xerogel powder, the lithium ion conductive polymer solid electrolyte solution, and a conductive auxiliary, having a stirring member inside, and using the stirring member as a cathode and a metal on the anode. Putting the mixed slurry in an electrolytic cell in which lithium is placed and performing electrolysis while operating the stirring member to form an electrolytic slurry containing lithium-containing vanadium pentoxide xerogel, and removing the solvent from the electrolytic slurry taken out of the electrolytic cell Rolled into a sheet with a roller press after removal of volatilization Making a chromatography bets, the positive electrode active material manufacturing method of positive active material for solid polymer electrolyte lithium battery, characterized in that the sheet to produce a positive active material for solid polymer electrolyte lithium battery having a predetermined shape from.