JP3751674B2 - Method for producing polymer electrolyte secondary battery - Google Patents

Description

前記表１から明らかなように本実施例１〜３により得られた二次電池は、比較例の二次電池に比べて放電容量維持率が極めて高いことがわかる。これは、実施例１〜３の二次電池は正極層がアルミニウム製パンチドメタルからなる多孔質集電体の上面側のみならず下面側にも回り込んだ構造を有し、正極層の多孔質集電体に対する密着力が向上された正極、負極層が銅製パンチドメタルからなる多孔質集電体の上面側のみならず下面側にも回り込んだ構造を有し、負極層の多孔質集電体に対する密着力が向上された負極のいずれか一方もしくは両者を備えているためである。
【００６４】
【発明の効果】
以上詳述したように、本発明によれば多孔質集電体に対して正極層および／または負極層を強固に密着させて充放電時における正極および／または負極のインピーダンスの上昇を防止し、充放電サイクル時の放電容量維持率を向上したポリマー電解質二次電池の製造方法を提供することができる。
【図面の簡単な説明】
【図１】本発明に係るポリマー電解質二次電池を示す斜視図。
【図２】本発明に係るポリマー電解質二次電池における正極の作製工程を説明するための斜視図。
【図３】図２の要部断面図。
【図４】本発明により作製された正極の断面図。
【符号の説明】
１…正極、
２…ポリマー電解質層、
３…負極、
４…ポリマー電解質二次電池
５、７…多孔質集電体、
６…正極層、
８…負極層
１１…裏当てシート、
１２…長尺多孔質集電体、
１４…ペースト塗布機構、
１７…ロール状ブレード、
１９…ペースト層、
２０…多孔質部（穴）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polymer electrolyte secondary battery including a solid polymer electrolyte layer.
[0002]
[Prior art]
In recent years, with the development of electronic devices, there has been a demand for the development of secondary batteries that are small and light, have high energy density, and that can be repeatedly charged and discharged. As such a secondary battery, a lithium secondary battery including a negative electrode using lithium or a lithium alloy as an active material and a positive electrode using an oxide, sulfide, or selenide such as molybdenum, vanadium, titanium, or niobium as an active material. Secondary batteries are known. However, a secondary battery including a negative electrode using lithium or a lithium alloy as an active material has a problem that the charge / discharge cycle life is short because lithium dendrites are generated in the negative electrode when the charge / discharge cycle is repeated.
[0003]
For this reason, a carbonaceous material that occludes and releases lithium ions, such as coke, graphite, carbon fiber, resin fired body, and pyrolytic vapor phase carbon, is used for the negative electrode. ₆ A nonaqueous solvent secondary battery using an electrolyte such as the above and an electrolyte solution composed of a nonaqueous solvent such as ethylene carbonate or propylene carbonate has been proposed. The non-aqueous solvent secondary battery can improve the deterioration of the negative electrode characteristics due to dendrite precipitation, and thus can improve the battery life and safety.
[0004]
On the other hand, US Pat. No. 5,296,318 describes a rechargeable lithium intercalation battery having a hybrid polymer electrolyte that is made flexible by adding polymer to the positive electrode, negative electrode, and electrolyte layer, A polymer electrolyte secondary battery is disclosed. Such a polymer electrolyte secondary battery is composed of a positive electrode in which an active material, a nonaqueous electrolytic solution and a positive electrode layer containing a polymer that holds the electrolytic solution are stacked on a current collector, and carbon that can occlude and release lithium ions in the current collector. A structure in which a solid polymer electrolyte layer including a nonaqueous electrolyte and a polymer holding the electrolyte is interposed between a porous material, a negative electrode including a nonaqueous electrolyte and a negative electrode layer containing a polymer holding the electrolyte Have
[0005]
By the way, the positive electrode is a porous current collector such as a punched metal, an active material such as a lithium manganese composite oxide, and an electrolytic solution such as a vinylidene fluoride-hexafluoropropylene (VDF-HFP) copolymer. After applying and drying a positive electrode paste containing a polymer that holds the electrolyte, impregnated with an electrolyte such as lithium hexafluorophosphate and a nonaqueous electrolyte solution including a nonaqueous solvent such as ethylene carbonate and propylene carbonate It is produced by forming a positive electrode layer on the porous current collector.
[0006]
However, a positive electrode having a positive electrode layer produced by simply applying a positive electrode paste to a porous current collector and drying it is inferior in adhesion of the positive electrode layer to the porous current collector.
[0007]
On the other hand, the negative electrode is like a copolymer of vinylidene fluoride-hexafluoropropylene (VDF-HFP) and an active material capable of occluding and releasing lithium ions such as carbon material in a porous current collector such as punched metal. A non-aqueous electrolyte solution comprising an electrolyte such as lithium hexafluorophosphate and a non-aqueous solvent such as ethylene carbonate and propylene carbonate after applying and drying a negative electrode paste containing a polymer that holds the electrolyte solution. And a negative electrode layer is formed on the porous current collector.
[0008]
However, a negative electrode having a negative electrode layer prepared by simply applying a negative electrode paste to a porous current collector and drying it has poor adhesion of the positive electrode layer to the porous current collector.
[0009]
Therefore, in the secondary battery manufactured by incorporating the above-described positive electrode and negative electrode together with the polymer electrolyte layer, there is a problem that the discharge capacity is remarkably reduced when charging and discharging are repeated.
[0010]
That is, in the polymer electrolyte secondary battery, the positive electrode layer, the negative electrode layer, and the solid polymer electrolyte layer that constitute the battery at the time of charging / discharging repeatedly expand and contract, so that the positive electrode layer peels off from the porous current collector or the porous Impedance increases due to peeling of the negative electrode layer from the current collector. As a result, there has been a problem that the discharge capacity is remarkably reduced with repeated charging and discharging. Particularly, a porous current collector such as an aluminum punched metal used as a positive electrode current collector is extremely inferior in adhesion to the positive electrode layer.
[0011]
[Problems to be solved by the invention]
The present invention provides a polymer electrolyte secondary that can prevent an increase in impedance of a positive electrode and / or a negative electrode during charge / discharge by firmly adhering a positive electrode layer and / or a negative electrode layer to a porous current collector An object of the present invention is to provide a battery manufacturing method.
[0012]
[Means for Solving the Problems]
The polymer electrolyte secondary battery according to the present invention includes a positive electrode in which a positive electrode layer containing a polymer that holds an active material and a non-aqueous electrolyte is stacked on a porous current collector, and a carbonaceous material that occludes and releases lithium ions in the current collector. A solid polymer electrolyte comprising a negative electrode in which a negative electrode layer containing a material and a polymer holding a non-aqueous electrolyte is laminated, and a polymer holding a non-aqueous electrolyte interposed between the positive electrode layer of the positive electrode and the negative electrode layer of the negative electrode In a method of manufacturing a polymer electrolyte secondary battery comprising a layer,
The positive electrode includes a step of superimposing a long porous current collector on a backing sheet so that the tension is lower than that of the backing sheet, and applying the paste to the long porous current collector and the backing sheet And supplying a positive electrode paste containing a polymer that holds an active material and a non-aqueous electrolyte from the upper surface side of the long porous current collector, and the long electrode coated with the positive electrode paste And the step of causing the paste applied on the upper surface side to wrap around to the lower surface side through the porous portion of the current collector. It is characterized by that.
[0013]
Another polymer electrolyte secondary battery according to the present invention includes a positive electrode in which a positive electrode layer containing a polymer that holds an active material and a non-aqueous electrolyte is stacked on a current collector, and occludes and releases lithium ions in a porous current collector. A solid including a negative electrode in which a negative electrode layer containing a polymer that holds a carbonaceous material and a non-aqueous electrolyte is laminated, and a polymer that holds a non-aqueous electrolyte interposed between the positive electrode layer of the positive electrode and the negative electrode layer of the negative electrode In a method for producing a polymer electrolyte secondary battery comprising a polymer electrolyte layer,
The negative electrode includes a step of overlapping a long porous current collector on a backing sheet so that the tension is lower than that of the backing sheet, and applying the paste to the long porous current collector and the backing sheet And supplying a negative electrode paste containing a carbonaceous material that occludes and releases lithium ions from the upper surface side of the long porous current collector and a polymer that holds a non-aqueous electrolyte, and a negative electrode paste. A step of causing the long porous current collector coated with sapphire to undulate by a difference in tension with the backing sheet and causing the paste coated on the upper surface side to wrap around the lower surface side through the porous portion of the current collector It is produced by the method containing these.
[0014]
Another polymer electrolyte secondary battery according to the present invention includes a positive electrode in which a positive electrode layer containing a polymer that holds an active material and a non-aqueous electrolyte is stacked on a porous current collector, and lithium ions are occluded and released from the current collector. A negative electrode layered with a negative electrode layer containing a carbonaceous material and a non-aqueous electrolyte-holding polymer, and a polymer holding a non-aqueous electrolyte interposed between the positive electrode layer of the positive electrode and the negative electrode layer of the negative electrode In a method for producing a polymer electrolyte secondary battery comprising a solid polymer electrolyte layer,
The positive electrode includes a step of superimposing a long porous current collector on a backing sheet so that the tension is lower than that of the backing sheet, and applying the paste to the long porous current collector and the backing sheet And supplying a positive electrode paste containing a polymer that holds an active material and a non-aqueous electrolyte from the upper surface side of the long porous current collector, and the long electrode coated with the positive electrode paste And the step of causing the paste applied on the upper surface side to wrap around to the lower surface side through the porous portion of the current collector. ,And
The negative electrode includes a step of overlapping a long porous current collector on a backing sheet so that the tension is lower than that of the backing sheet, and applying the paste to the long porous current collector and the backing sheet And supplying a negative electrode paste containing a carbonaceous material that occludes and releases lithium ions from the upper surface side of the long porous current collector and a polymer that holds a non-aqueous electrolyte, and a negative electrode paste. A step of causing the long porous current collector coated with sapphire to undulate by a difference in tension with the backing sheet and causing the paste coated on the upper surface side to wrap around the lower surface side through the porous portion of the current collector It is produced by a method including
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a method for producing a polymer electrolyte secondary battery according to the present invention will be described in detail with reference to FIGS.
As shown in FIG. 1, a polymer electrolyte secondary battery 4 is manufactured by laminating a positive electrode 1, a solid polymer electrolyte layer 2 and a negative electrode 3. The positive electrode 1 has a structure in which a positive electrode layer 6 is supported on a porous current collector 5. The negative electrode 3 has a structure in which a negative electrode layer is supported on a porous current collector 7.
[0016]
Next, a method for producing the positive electrode 1 and the negative electrode 3 and a configuration of the solid polymer electrolyte layer 3 will be described.
1) Method for producing positive electrode 1
First, as shown in FIG. 2, a long porous current collector 12 made of, for example, aluminum punched metal is overlapped on the backing sheet 11 so that the tension is lower than that of the backing sheet 11, and a pair of feeds are made. It is sent to the paste application mechanism 14 through the roll 13. The coating mechanism 14 is disposed near the upper surface of the long porous current collector 12 in the width direction thereof, and has a paste supply container 15 having an opening at the bottom, and a transport roll rotated in a clockwise direction. 16 and a roll-shaped blade 17 which is disposed above the roll 16 with a desired interval and whose lower part is notched in the length direction. The supply container 15 contains a positive electrode paste containing an active material, a conductive material, a polymer for holding a non-aqueous electrolyte, and a plasticizer such as DBP (dibutyl phthalate). When the long porous current collector 12 and the backing sheet 11 are sent to the paste application mechanism 14, the positive electrode paste is supplied from the supply container 15 to the upper surface of the long porous current collector 12. A paste layer 18 having a desired thickness is formed, and further passes through between the conveying roll 16 and the roll-shaped blade 17, so that excess paste is scraped off by the roll-shaped blade 17 and a certain amount of paste layer 19 is formed. Is applied to the upper surface of the long porous current collector 12. The long porous current collector 12 coated with the paste layer 19 that has passed between the transport roll 16 and the roll blade 17 is waved by a difference in tension with the backing sheet 11. For this reason, the long porous current collector 12 is partially separated from the lower backing sheet 11 as shown in FIG. 3, and the paste applied on the upper surface side has a large number of pores. It goes around to the lower surface side through the mass part (hole) 20. Thus, the long porous current collector 12 in which the paste applied on the upper surface side wraps around the lower surface side is sent together with the backing sheet 11 to a drying furnace (not shown), and the paste is dried. Pressure is applied accordingly.
[0017]
By going through the steps described above, the positive electrode layer 6 is formed not only on the upper surface of the porous current collector 5 shown in FIG. 4 but also on the lower surface side through the porous portion (hole) 20. Thereafter, by immersing the structure shown in FIG. 4 in a non-aqueous electrolyte, the polymer in the positive electrode layer is held by the electrolyte and the plasticizer in the positive electrode layer is replaced with the electrolyte. After the positive electrode layer is impregnated with an electrolytic solution or the plasticizer in the positive electrode layer is removed by extraction with a solvent such as ethanol, the positive electrode layer is impregnated with a non-aqueous electrolytic solution to produce a positive electrode To do.
[0018]
The backing sheet 11 is made of, for example, a polymer resin such as polyethylene terephthalate (PET) or polypropylene, or a metal such as copper or aluminum.
[0019]
In order to lower the tension of the long porous current collector 12 than the backing sheet 11, for example, a method of applying back tension only to the backing sheet 11, the backing sheet 11 is made of the long porous sheet. A method of applying a back tension stronger than that of the mass collector 12 can be adopted. The tension difference may be appropriately selected depending on the form of the porous current collector 12, the material of the backing sheet 11, and the like.
[0020]
As the porous current collector, aluminum mesh, aluminum expanded metal, and the like can be used in addition to Al punched metal.
Examples of the active material constituting the positive electrode layer 6 include various oxides (for example, LiMn ₂ O _Four Lithium manganese composite oxide such as manganese dioxide, for example LiNiO ₂ Lithium-containing nickel oxides such as LiCoO ₂ And lithium-containing cobalt oxide, lithium-containing nickel cobalt oxide, lithium-containing amorphous vanadium pentoxide, and the like) and chalcogen compounds (for example, titanium disulfide and molybdenum disulfide). Of these, lithium manganese composite oxide, lithium-containing cobalt oxide, and lithium-containing nickel oxide are preferably used.
[0021]
Examples of the conductive material constituting the positive electrode layer 6 include artificial graphite, carbon black (for example, acetylene black), nickel powder, and the like.
[0022]
The plasticizer contained in the positive electrode layer 6 is added for the purpose of improving mechanical properties such as the strength of the solid electrolyte layer and improving the charge / discharge characteristics by increasing the amount of electrolyte impregnation.
Examples of the polymer holding the non-aqueous electrolyte constituting the positive electrode layer 6 include polyethylene oxide derivatives, polypropylene oxide derivatives, polymers containing the derivatives, vinylidene fluoride (VdF) and hexafluoropropylene (HFP). A polymer or the like can be used. In the positive electrode layer, such a polymer may exist in a form in which molecules are cross-linked. In the copolymer, VdF contributes to the improvement of mechanical strength at the skeleton of the copolymer, and HFP is incorporated into the copolymer in an amorphous state, thereby maintaining the non-aqueous electrolyte and lithium. It functions as an ion transmission part. The copolymerization ratio of HFP is usually about 20% by weight at the maximum although it depends on the method for synthesizing the copolymer.
[0023]
The nonaqueous electrolytic solution constituting the positive electrode layer 6 is prepared by dissolving an electrolyte in a nonaqueous solvent.
Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (γ- BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like. The non-aqueous solvent may be used alone or in combination of two or more.
[0024]
Examples of the electrolyte include lithium perchlorate (LiClO). _Four ), Lithium hexafluorophosphate (LiPF) ₆ ), Lithium boron tetrafluoride (LiBF) _Four ), Lithium hexafluoroarsenide (LiAsF) ₆ ), Lithium trifluoromethanesulfonate (LiCF) _Three SO _Three ), Bistrifluoromethylsulfonylimide lithium [LiN (CF _Three SO _Three ) ₂ And the like.
[0025]
The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.2 mol / l to 2 mol / l.
Note that the paste applying means used in the present invention is not limited to the structure shown in FIG. 2 described above. In short, a positive or negative paste can be applied to a long porous current collector disposed on a backing sheet. Any structure can be used.
[0026]
2) Method for producing negative electrode 3
This negative electrode 3 uses a carbonaceous material that absorbs and releases lithium ions as a negative electrode paste, a polymer that contains an electrolyte solution, and a plasticizer such as DBP (dibutyl phthalate). The body is manufactured by a method substantially similar to the method for manufacturing the positive electrode described above except that the body is, for example, a copper punched metal.
[0027]
That is, a long porous current collector made of, for example, copper punched metal is superimposed on the backing sheet so that the tension is lower than that of the backing sheet, and the structure shown in FIG. Send to paste application mechanism. A negative electrode paste containing a carbonaceous material that occludes and releases lithium ions, a polymer that holds an electrolytic solution, and a plasticizer such as DBP (dibutyl phthalate) is accommodated in the supply container of the paste application mechanism. When the long porous current collector and the backing sheet are sent to the paste application mechanism, the negative electrode paste is supplied from the supply container 15 to the upper surface of the long porous current collector, and the desired thickness is obtained. The paste layer is formed, and further, the excess paste is scraped by the roll-shaped blade by passing between the transport roll and the roll-shaped blade, so that a certain amount of the paste layer becomes the long porous current collector. It is applied to the upper surface of the body. The long porous current collector coated with the paste layer that has passed between the transport roll and the roll-shaped blade is waved by a difference in tension with the backing sheet. For this reason, the long porous current collector is partially separated from the backing sheet on the lower side, as in FIG. 3 described above, and the paste applied on the upper surface side has a large number of porous current collectors. Go through the part (hole) to the bottom side. The long porous current collector in which the paste applied on the upper surface side wraps around on the lower surface side is sent to a drying furnace (not shown) together with the backing sheet, the paste is dried, and further if necessary. Pressurized.
[0028]
Through the steps described above, as in FIG. 4 described above, a negative electrode layer is formed that wraps around not only the upper surface of the porous current collector but also the lower surface side through the porous portion (hole). Thereafter, by immersing the structure shown in FIG. 4 in a nonaqueous electrolytic solution, the polymer in the negative electrode layer is held by the electrolytic solution, and the plasticizer and the electrolytic solution in the negative electrode layer are replaced, The negative electrode layer is impregnated with an electrolytic solution, or the plasticizer in the negative electrode layer is removed by extraction with a solvent such as ethanol, and then the negative electrode layer is impregnated with a nonaqueous electrolytic solution to produce a positive electrode. To do.
[0029]
As the porous current collector, a copper mesh, a copper expanded metal, or the like can be used in addition to the copper punched metal.
Examples of the carbonaceous material that occludes and releases lithium ions constituting the negative electrode layer include those obtained by firing organic polymer compounds (for example, phenol resin, polyacrylonitrile, cellulose, etc.), coke, and pitch. The carbonaceous material represented by what is obtained by baking, artificial graphite, natural graphite, etc. can be mentioned. Among them, it is preferable to use a carbonaceous material obtained by firing the organic polymer compound at a temperature of 500 ° C. to 3000 ° C. under an inert gas atmosphere such as argon gas or nitrogen gas at normal pressure or reduced pressure. preferable.
[0030]
As the polymer and the non-aqueous electrolyte, the same ones as those described for the positive electrode are used.
The negative electrode layer is allowed to contain conductive materials such as artificial graphite, natural graphite, carbon black, acetylene black, ketjen black, nickel powder, and polyphenylene derivatives, and fillers such as olefin polymers and carbon fibers.
[0031]
In addition, any one of the said positive electrode 1 and the negative electrode 3 is produced by the method of (1-1)-(1-4) demonstrated below; The method of (2-1)-(2-4); Is acceptable.
[0032]
(1-1) A polymer solution holding the non-aqueous electrolyte is prepared, and a plasticizer such as DBP (dibutyl phthalate), the active material, and the conductive material are added to the solution, and then mixed. After forming the positive electrode layer by film formation, the positive electrode layer and the current collector are bonded by, for example, thermocompression bonding. The electrolyte is retained in the polymer by immersing it in a non-aqueous electrolyte and the positive electrode layer is impregnated with the electrolyte by replacing the plasticizer and the electrolyte in the positive electrode layer, or After the plasticizer in the positive electrode layer is removed by extraction with a solvent such as ethanol, the positive electrode layer is impregnated with a non-aqueous electrolyte to produce a positive electrode.
[0033]
(1-2) A polymer solution holding the non-aqueous electrolyte is prepared, and a plasticizer such as DBP (dibutyl phthalate), the active material, and the conductive material are added to the solution, and then mixed. A positive electrode paint is prepared. The positive electrode paint is applied to the current collector and then dried. The electrolyte is retained in the polymer by immersing it in a non-aqueous electrolyte and the positive electrode layer is impregnated with the electrolyte by replacing the plasticizer and the electrolyte in the positive electrode layer, or After the plasticizer in the positive electrode layer is removed by extraction with a solvent such as ethanol, the positive electrode layer is impregnated with a non-aqueous electrolyte to produce a positive electrode.
[0034]
(1-3) A polymer solution holding the non-aqueous electrolyte was prepared, and after adding the active material and the conductive material to the solution, they were mixed and formed into a positive electrode layer. Thereafter, the positive electrode layer and the current collector are bonded to each other by, for example, thermocompression bonding, and impregnated with a non-aqueous electrolyte to produce a positive electrode.
[0035]
(1-4) A polymer solution holding the non-aqueous electrolyte is prepared, and the active material and the conductive material are added to the solution, and then mixed to prepare a positive electrode paint. The positive electrode coating material is applied to the current collector, dried, and impregnated with a non-aqueous electrolyte to produce a positive electrode.
[0036]
(2-1) A polymer solution holding the non-aqueous electrolyte is prepared, and a plasticizer such as DBP (dibutyl phthalate) and the active material are added to the solution, and then mixed to form a film. After producing a negative electrode layer by this, the said negative electrode layer and the said collector are adhere | attached, for example by thermocompression bonding. The electrolyte is held in the polymer by immersing it in a non-aqueous electrolyte and the negative electrode layer is impregnated with the electrolyte by replacing the plasticizer and the electrolyte in the negative electrode layer, or After the plasticizer in the negative electrode layer is removed by extraction with a solvent such as ethanol, a negative electrode is produced by impregnating with a non-aqueous electrolyte.
[0037]
(2-2) A polymer solution holding the non-aqueous electrolyte is prepared, and a plasticizer such as DBP (dibutyl phthalate) and the active material are added to the solution. To prepare. The negative electrode coating material is applied to the current collector and then dried. The electrolyte is held in the polymer by immersing it in a non-aqueous electrolyte and the negative electrode layer is impregnated with the electrolyte by replacing the plasticizer and the electrolyte in the negative electrode layer, or After the plasticizer in the negative electrode layer is removed by extraction with a solvent such as ethanol, a negative electrode is produced by impregnating with a non-aqueous electrolyte.
[0038]
(2-3) After preparing the polymer solution holding the non-aqueous electrolyte, adding the active material to the solution, mixing them, and forming a negative electrode layer by forming a film, the negative electrode The layer and the current collector are bonded by, for example, thermocompression bonding. A negative electrode is produced by impregnating this with a non-aqueous electrolyte.
[0039]
(2-4) A polymer solution holding the non-aqueous electrolyte is prepared, the active material is added to the solution, and then mixed to prepare a negative electrode paint. After the negative electrode coating material is applied to the current collector, it is dried and impregnated with a non-aqueous electrolyte to produce a negative electrode.
[0040]
3) Solid polymer electrolyte layer 2
The polymer electrolyte layer 2 includes a non-aqueous electrolyte and a polymer that holds the electrolyte.
[0041]
The non-aqueous electrolyte and the polymer are the same as those described for the positive electrode described above.
The solid electrolyte layer 2 can be produced, for example, by the method described below.
[0042]
(1) A polymer solution for holding the non-aqueous electrolyte is prepared, a plasticizer such as DBP (dibutyl phthalate) is added to the solution, and this is formed into a film and dried. A polymer electrolyte layer is produced by immersing in, allowing the polymer to hold the electrolyte, and impregnating the electrolyte by replacing the plasticizer and the electrolyte.
[0043]
(2) A polymer solution holding the non-aqueous electrolyte is prepared, and a plasticizer such as DBP (dibutyl phthalate) is added to the solution. After film formation and drying, the plasticizer is ethanol or the like. The polymer electrolyte layer is prepared by removing the solution by extraction with a solvent, and then impregnating it with a non-aqueous electrolyte.
[0044]
(3) A polymer solution that holds the non-aqueous electrolyte is prepared, and after film formation and drying, a polymer electrolyte layer is produced by impregnating the non-aqueous electrolyte.
In the methods (1) and (2), the plasticizer is added for the purpose of improving mechanical characteristics such as the strength of the solid electrolyte layer and improving the amount of electrolyte impregnation to improve the charge / discharge characteristics. After the plasticizer is added, a film is formed, and the amount of electrolytic solution impregnation can be increased by impregnating the polymer electrolyte layer with the nonaqueous electrolytic solution so that the plasticizer and the nonaqueous electrolytic solution are replaced. .
[0045]
In the secondary battery manufacturing method, the electrolytic solution impregnation (including the removal of the plasticizer in the case of adding a plasticizer) may be performed after the secondary battery not impregnated with the electrolytic solution is assembled. The method for producing a polymer electrolyte secondary battery according to the present invention described above includes a step of superimposing a long porous current collector on a backing sheet so that tension is lower than that of the backing sheet; A positive electrode including a polymer that holds an active material and a non-aqueous electrolyte from the upper surface side of the long porous current collector by supplying the porous current collector and the backing sheet to a paste coating means (paste coating mechanism) And applying the paste applied to the upper surface side of the elongated porous current collector coated with the positive electrode paste by the tension difference with the backing sheet. The positive electrode is produced by a method including a step of wrapping around the lower surface through the porous portion. The positive electrode produced by such a method has the positive electrode layer 6 which is not only on the upper surface of the porous current collector 5 but also on the lower surface side through the porous portion (hole) 20 as shown in FIG. 4 described above. For this reason, the positive electrode layer 6 firmly adhered to the porous current collector 5 is provided. Therefore, by manufacturing the polymer electrolyte secondary battery having the structure shown in FIG. 1 using the positive electrode, even if the positive electrode layer expands or contracts during repeated charge and discharge, the positive electrode is used as the positive electrode. Peeling of the layer can be avoided and an increase in impedance can be prevented. As a result, a high discharge capacity can be maintained even after repeated charging and discharging, and a polymer electrolyte secondary battery having excellent cycle characteristics can be obtained.
[0046]
Further, another method for producing a polymer electrolyte secondary battery according to the present invention includes a step of superimposing a long porous current collector on a backing sheet so that the tension is lower than that of the backing sheet; Carbonaceous material and non-aqueous electrolyte that supply the porous current collector and backing sheet to paste application means (paste application mechanism) and occlude and release lithium ions from the upper surface side of the long porous current collector A negative electrode paste containing a polymer for holding the negative electrode, and the long porous current collector coated with the negative electrode paste is applied to the upper surface of the long current collector by undulation due to a difference in tension with the backing sheet. A negative electrode is produced by a method including a step of passing the paste past the lower surface side through the porous portion of the current collector. Since the negative electrode produced by such a method has a negative electrode layer that wraps around not only the upper surface of the porous current collector but also the lower surface side through the porous portion (hole), as in FIG. It has a negative electrode layer firmly adhered to the mass collector. Therefore, by manufacturing the polymer electrolyte secondary battery having the structure shown in FIG. 1 using the negative electrode, even if the negative electrode layer expands or contracts during repeated charge / discharge, the negative electrode is removed from the porous current collector. Peeling of the layer can be avoided and an increase in impedance can be prevented. As a result, a high discharge capacity can be maintained even after repeated charging and discharging, and a polymer electrolyte secondary battery having excellent cycle characteristics can be obtained.
[0047]
Furthermore, by producing the positive electrode and the negative electrode by the method described above, and manufacturing the polymer electrolyte secondary battery having the structure shown in FIG. 1 using the positive electrode and the negative electrode, the positive electrode layer and the negative electrode layer are repeatedly charged and discharged. Even if the material expands or contracts, it is possible to avoid the separation of the positive electrode layer and the negative electrode layer from the porous current collector, and it is possible to more effectively prevent an increase in impedance. As a result, even when charging and discharging are repeated, a high discharge capacity can be maintained, and a polymer electrolyte secondary battery with further excellent cycle characteristics can be obtained.
[0048]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings described above.
<Preparation of positive electrode A>
After dissolving 2.8 g of a vinylidene fluoride-hexafluoropropylene (VdF-HFP) copolymer (trade name, manufactured by Elfatochem; KYNAR2801, copolymerization ratio [VdF: HFP] is 88:12) in 20 g of acetone, In this acetone solution, 4.3 g of dibutyl phthalate (DBP), and the composition formula is LiCoO as an active material. ₂ A paste paint for a positive electrode was prepared by adding 10.5 g of a lithium-containing cobalt oxide (manufactured by Nippon Heavy Chemical Industry) represented by
[0049]
Next, as shown in FIG. 2, a long porous current collector 12 made of an aluminum punched metal having a thickness of 30 μm was superposed on a backing sheet 11 made of PET and having a thickness of 15 μm. At this time, the tension of the long porous current collector 12 is 0.3 kgf, the tension of the backing sheet 11 is 1.2 kgf, and the tension of the long porous current collector 12 is the backing sheet. 11 smaller than that. The laminated backing sheet 11 and the long porous current collector 12 were sent to the paste application mechanism 14 through a pair of feed rolls 13. At this time, the positive electrode paste prepared by the above method was accommodated in the supply container 15 of the paste application mechanism 14. By sending the long porous current collector 12 and the backing sheet 11 to the paste application mechanism 14, the positive electrode paste is supplied from the supply container 15 to the upper surface of the long porous current collector 12. Then, a paste layer 18 having a desired thickness is formed, and further, the paste paste 18 is scraped off by the roll-shaped blade 17 by passing between the transport roll 16 and the roll-shaped blade 17 so that a certain basis weight (2 .5 mAh / cm ² ) Paste layer 19 was applied to the upper surface of the long porous current collector 12. The long porous current collector 12 coated with the paste layer 19 that passed between the transport roll 16 and the roll blade 17 was waved due to a difference in tension with the backing sheet 11. For this reason, the long porous current collector 12 is partially separated from the lower backing sheet 11 as shown in FIG. 3, and the paste applied on the upper surface side has a large number of pores. It goes around to the lower surface side through the mass part (hole) 20. The long porous current collector 12 in which the paste applied on the upper surface side wraps around on the lower surface side is sent to a drying furnace (not shown) together with the backing sheet 11 so that the paste is dried and further pressurized. It was done. Through the steps described above, non-aqueous electrolyte non-impregnated having the positive electrode layer 6 wrapping around not only the upper surface of the porous current collector 5 shown in FIG. 4 but also the lower surface side through the porous portion (hole) 20. A positive electrode was produced.
[0050]
<Preparation of positive electrode B>
First, a long porous current collector made of an aluminum punched metal having a thickness of 30 μm was superposed on a backing sheet made of PET and having a thickness of 15 μm. At this time, the long porous current collector and the backing sheet were set to the same tension. The laminated backing sheet and the long porous current collector were sent to the paste applying mechanism having the structure shown in FIG. 5 through a pair of feed rolls. At this time, the same positive electrode paste as the positive electrode A was accommodated in the supply container of the paste application mechanism. By sending the long porous current collector and the backing sheet to the paste application mechanism, the positive electrode paste is supplied from the supply container to the upper surface of the long porous current collector, and has a desired thickness. The paste layer is further formed, and the excess paste is scraped off by the roll-shaped blade by passing between the transport roll and the roll-shaped blade, and a fixed basis weight (2.5 mAh / cm ² ) Paste layer was applied to the upper surface of the long porous current collector. The long porous current collector coated with the paste layer that has passed between the transport roll and the roll-shaped blade is sent to a drying furnace with the lower surface in close contact with the backing sheet, and the paste is dried. And further pressurized. Through the steps described above, a non-aqueous electrolyte non-impregnated positive electrode having a positive electrode layer only on the upper surface of the porous current collector was produced.
[0051]
Each of the obtained positive electrode A and positive electrode B was cut into a size of 1 cm × 10 cm, and the peel strength of the positive electrode layer with respect to the porous current collector was measured. As a result, the peel strength of the positive electrode A was 43 gf, The peel strength of B was 12 gf, and it was confirmed that the positive electrode A had a higher peel strength than the positive electrode B.
[0052]
<Preparation of negative electrode A>
A vinylidene fluoride-hexafluoropropylene copolymer (2.0 g) similar to that used for the positive electrode was dissolved in acetone (12 g) to prepare an acetone solution, and dibutyl phthalate (DBP) (3.12 g) was added to the acetone solution. Then, 7.37 g of mesophase pitch carbon fiber (manufactured by Petka Co., Ltd.) was added as an active material and mixed to prepare a negative electrode paste.
[0053]
Next, a long porous current collector made of 20 μm thick copper punched metal was superimposed on a 15 μm thick backing sheet made of PET. At this time, the tension of the long porous current collector is 0.3 kgf, the tension of the backing sheet is 1.2 kgf, and the tension of the long porous current collector is that of the backing sheet. I made it smaller. The laminated backing sheet and the long porous current collector were sent to a paste application mechanism having the same structure as that shown in FIG. At this time, the negative electrode paste prepared by the above method was accommodated in the supply container of the paste application mechanism. By sending the long porous current collector and the backing sheet to the paste application mechanism, the negative electrode paste is supplied from the supply container to the upper surface of the long porous current collector to obtain a desired thickness. A paste layer is formed, and the paste is further scraped off by the roll-shaped blade by passing between the transport roll and the roll-shaped blade, and a certain basis weight (2.5 mAh / cm ² ) Paste layer was applied to the upper surface of the long porous current collector. The long porous current collector coated with the paste layer that passed between the transport roll and the roll blade was waved due to a difference in tension with the backing sheet. For this reason, the long porous current collector is partially separated from the backing sheet on the lower side, as in FIG. 3 described above, and the paste applied on the upper surface side has a large number of porous current collectors. Go through the part (hole) to the bottom side. The long porous current collector in which the paste applied on the upper surface side wraps around the lower surface side is sent to a drying furnace (not shown) together with the backing sheet, and the paste is dried and further pressurized. . Through the steps described above, as in FIG. 4 described above, the non-aqueous electrolyte solution is not impregnated with a negative electrode layer that is wound not only on the upper surface of the porous current collector but also on the lower surface side through the porous portion (hole). A negative electrode was produced.
[0054]
<Preparation of negative electrode B>
First, a long porous current collector made of copper punched metal having a thickness of 20 μm was overlapped on a backing sheet made of PET and having a thickness of 15 μm. At this time, the long porous current collector and the backing sheet were set to the same tension. The laminated backing sheet and the long porous current collector were sent to the paste applying mechanism having the structure shown in FIG. 5 through a pair of feed rolls. At this time, the same negative electrode paste as the negative electrode A was accommodated in the supply container of the paste application mechanism. By sending the long porous current collector and the backing sheet to the paste application mechanism, the negative electrode paste is supplied from the supply container to the upper surface of the long porous current collector to obtain a desired thickness. The paste layer is further formed, and the excess paste is scraped off by the roll-shaped blade by passing between the transport roll and the roll-shaped blade, and a fixed basis weight (2.5 mAh / cm ² ) Paste layer was applied to the upper surface of the long porous current collector. The long porous current collector coated with the paste layer that has passed between the transport roll and the roll-shaped blade is sent to a drying furnace with the lower surface in close contact with the backing sheet, and the paste is dried. And further pressurized. Through the steps described above, a non-aqueous electrolyte non-impregnated negative electrode having a negative electrode layer only on the upper surface of the porous current collector was produced.
[0055]
The obtained negative electrode A and negative electrode B were each cut into a size of 1 cm × 10 cm, and the peel strength of the negative electrode layer with respect to the porous current collector was measured. As a result, the peel strength of the negative electrode A was 57 gf, The peel strength of B was 15 gf, and it was confirmed that the negative electrode A had a higher peel strength than the negative electrode B.
[0056]
<Preparation of solid polymer electrolyte layer>
A vinylidene fluoride-hexafluoropropylene copolymer (2.0 g) similar to that used for the positive electrode was dissolved in 10 g of acetone to prepare an acetone solution, and then dibutyl phthalate (DBP) 2. After adding 0 g, the coating for electrolyte layer was prepared by mixing. The paint was applied onto a smooth glass plate so that the film thickness after drying was 70 μm, and then dried in the same manner as the positive and negative electrodes, and peeled off from the glass plate to produce a solid polymer electrolyte layer.
[0057]
<Preparation of non-aqueous electrolyte>
LiPF as an electrolyte in a non-aqueous solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) are mixed at a volume ratio of 1: 1. ₆ Was dissolved to a concentration of 1 mol / l to prepare a non-aqueous electrolyte.
[0058]
(Example 1)
The positive electrode A and the negative electrode B were cut to a size of 2 cm × 2 cm, and the solid polymer electrolyte layer was cut to a size of 2.25 cm × 2.25 cm. The polymer electrolyte layer is interposed between the positive electrode and the negative electrode, and these are laminated by thermocompression bonding with a rigid roll heated to 130 ° C., as shown in FIG. 1, and immersed in the non-aqueous electrolyte. Thus, a non-aqueous electrolyte was impregnated to produce a polymer electrolyte secondary battery.
[0059]
(Example 2)
A polymer electrolyte secondary battery was produced in the same manner as in Example 1 except that the positive electrode B and the negative electrode A were used.
[0060]
(Example 3)
A polymer electrolyte secondary battery was produced in the same manner as in Example 1 except that the positive electrode A and the negative electrode A were used.
[0061]
(Comparative example)
A polymer electrolyte secondary battery was produced in the same manner as in Example 1 except that the positive electrode B and the negative electrode B were used.
[0062]
About the obtained secondary batteries of Examples 1 to 3 and Comparative Example, after charging with a constant current and a constant voltage of 10 mA for a charging current of 2 mA, 4.2 V, charging and discharging with a current of 2 mA up to 2.7 V Was repeated. The discharge capacity retention ratio with respect to the initial discharge capacity after repeating 100 times of charge / discharge was measured. The results are shown in Table 1 below.
[0063]

As can be seen from Table 1, the secondary batteries obtained in Examples 1 to 3 have an extremely high discharge capacity retention rate compared to the secondary battery of the comparative example. This is because the secondary batteries of Examples 1 to 3 have a structure in which the positive electrode layer wraps around not only the upper surface side but also the lower surface side of the porous current collector made of aluminum punched metal. Positive electrode with improved adhesion to the current collector, negative electrode layer has a structure that wraps around not only the upper surface side but also the lower surface side of the porous current collector made of copper punched metal, and the negative electrode layer is porous This is because one or both of the negative electrodes with improved adhesion to the current collector are provided.
[0064]
【The invention's effect】
As described above in detail, according to the present invention, the positive electrode layer and / or the negative electrode layer are firmly adhered to the porous current collector to prevent an increase in the impedance of the positive electrode and / or the negative electrode during charge / discharge, The manufacturing method of the polymer electrolyte secondary battery which improved the discharge capacity maintenance factor at the time of a charging / discharging cycle can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a polymer electrolyte secondary battery according to the present invention.
FIG. 2 is a perspective view for explaining a production process of a positive electrode in a polymer electrolyte secondary battery according to the present invention.
3 is a cross-sectional view of the main part of FIG.
FIG. 4 is a cross-sectional view of a positive electrode manufactured according to the present invention.
[Explanation of symbols]
1 ... positive electrode,
2 ... polymer electrolyte layer,
3 ... negative electrode,
4 ... Polymer electrolyte secondary battery
5, 7 ... porous current collector,
6 ... positive electrode layer,
8 ... Negative electrode layer
11 ... backing sheet,
12 ... Long porous current collector,
14 ... paste application mechanism,
17 ... roll blade,
19 ... paste layer,
20: Porous part (hole).

Claims (3)

A positive electrode in which a positive electrode layer containing a polymer that holds an active material and a non-aqueous electrolyte is laminated on a porous current collector, a carbonaceous material that absorbs and releases lithium ions in the current collector, and a polymer that holds a non-aqueous electrolyte. A polymer electrolyte secondary battery comprising: a negative electrode having a negative electrode layer laminated thereon; and a positive electrode layer of the positive electrode and a solid polymer electrolyte layer containing a polymer that holds a non-aqueous electrolyte interposed between the negative electrode layer of the negative electrode In the manufacturing method,
The positive electrode includes a step of superimposing a long porous current collector on a backing sheet so that the tension is lower than that of the backing sheet, and applying the paste to the long porous current collector and the backing sheet And supplying a positive electrode paste containing a polymer that holds an active material and a non-aqueous electrolyte from the upper surface side of the long porous current collector, and the long electrode coated with the positive electrode paste And the step of causing the paste applied on the upper surface side to wrap around to the lower surface side through the porous portion of the current collector. A method for producing a polymer electrolyte secondary battery. A positive electrode in which a positive electrode layer containing a polymer that holds an active material and a non-aqueous electrolyte is laminated on a current collector, a carbonaceous material that absorbs and releases lithium ions in a porous current collector, and a polymer that holds a non-aqueous electrolyte A polymer electrolyte secondary battery comprising: a negative electrode having a negative electrode layer laminated thereon; and a positive electrode layer of the positive electrode and a solid polymer electrolyte layer containing a polymer that holds a non-aqueous electrolyte interposed between the negative electrode layer of the negative electrode In the manufacturing method,
The negative electrode includes a step of overlapping a long porous current collector on a backing sheet so that the tension is lower than that of the backing sheet, and applying the paste to the long porous current collector and the backing sheet And supplying a negative electrode paste containing a carbonaceous material that occludes and releases lithium ions from the upper surface side of the long porous current collector and a polymer that holds a non-aqueous electrolyte, and a negative electrode paste. A step of causing the long porous current collector coated with sapphire to undulate by a difference in tension with the backing sheet and causing the paste coated on the upper surface side to wrap around the lower surface side through the porous portion of the current collector A method for producing a polymer electrolyte secondary battery, comprising: A positive electrode in which a positive electrode layer containing a polymer that holds an active material and a non-aqueous electrolyte is laminated on a porous current collector, a carbonaceous material that absorbs and releases lithium ions in the current collector, and a polymer that holds a non-aqueous electrolyte. A polymer electrolyte secondary battery comprising: a negative electrode having a negative electrode layer laminated thereon; and a positive electrode layer of the positive electrode and a solid polymer electrolyte layer containing a polymer that holds a non-aqueous electrolyte interposed between the negative electrode layer of the negative electrode In the manufacturing method,
The positive electrode includes a step of superimposing a long porous current collector on a backing sheet so that the tension is lower than that of the backing sheet, and applying the paste to the long porous current collector and the backing sheet And supplying a positive electrode paste containing a polymer that holds an active material and a non-aqueous electrolyte from the upper surface side of the long porous current collector, and the long electrode coated with the positive electrode paste And the step of causing the paste applied on the upper surface side to wrap around the lower surface side through the porous portion of the current collector by making the porous current collector corrugate due to a difference in tension with the backing sheet. And the negative electrode includes a step of superimposing a long porous current collector on a backing sheet so that the tension is lower than that of the backing sheet; and the long porous current collector and the backing sheet. For paste application means for negative electrode And applying a paste containing a carbonaceous material that occludes and releases lithium ions from the upper surface side of the long porous current collector and a polymer that holds a non-aqueous electrolyte, and a negative electrode paste was applied And a step of causing the long porous current collector to swell due to a difference in tension with the backing sheet and causing the paste applied on the upper surface side to wrap around the lower surface side through the porous portion of the current collector. A method for producing a polymer electrolyte secondary battery, wherein

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