WO2021100360A1

WO2021100360A1 - Pre-doped sheet for power storage device and production method therefor

Info

Publication number: WO2021100360A1
Application number: PCT/JP2020/038618
Authority: WO
Inventors: 慎青山; 裕太柿本
Original assignee: テイカ株式会社
Priority date: 2019-11-19
Filing date: 2020-10-13
Publication date: 2021-05-27
Also published as: JPWO2021100360A1

Abstract

Provided is a pre-doped sheet that is for a power storage device and that contains a pre-doping agent containing a lithium metal composite oxide, the pre-doped sheet for a power storage device characterized in that: the lithium metal composite oxide contains lithium (Li) and at least one metallic element (Me) selected from the group consisting of Fe, Al, Mn, and Co; the lithium metal composite oxide has an antifluorite structure; the Li/Me ratio (molar ratio) in the lithium metal composite oxide fulfills 3.0 < Li/Me ≤ 7.5; and the content (X) of the pre-doping agent fulfills 0.3 < X < 6.0 mg/cm². Provided thereby is a pre-doped sheet for a power storage device in which pre-doping can be performed effectively without including a pre-doping agent in an electrode and which contains a lithium metal composite oxide that has an antifluorite structure and that can be used appropriately as a power storage device having excellent rate capability while maintaining electrode strength.

Description

Pre-doped sheet for power storage device and its manufacturing method

The present invention relates to a pre-doped sheet used in a power storage device such as a lithium ion battery, a lithium ion capacitor, and an electric double layer capacitor.

In power storage devices such as lithium ion batteries, lithium ion capacitors, and electric double layer capacitors, it is known that the negative electrode is pre-doped with lithium ions to lower the potential of the negative electrode, thereby enabling high volume energy density of the power storage device. ing. In recent years, a method has been proposed in which a metal foil having a plurality of through holes is used in a current collector, and lithium ions are pre-doped into the negative electrode via an electrolytic solution by arranging the metal lithium foil in an electrode in which a large number of positive electrodes and negative electrodes are laminated. Has been done.

Patent Document 1 describes an electrode including an electrode current collector having a plurality of through holes, an electrode mixture layer provided in the electrode current collector, and an electrode mixture connected to the electrode current collector. The electrode current collector has a first region having an ion supply source for supplying ions to the layer and having a predetermined through-hole opening ratio, and a second region having a through-hole opening ratio larger than that of the first region. The storage device is described, wherein the first region is an edge portion of the electrode current collector, and the second region is a central portion of the electrode current collector. A lithium electrode is incorporated in the power storage device, and the lithium electrode has a lithium electrode current collector to which a metallic lithium foil as an ion supply source is crimped, and lithium is injected by injecting an electrolytic solution. It is described that lithium ions are pre-doped from the electrode to the negative electrode. According to this, it is possible to adjust the permeation state of the electrolytic solution, and it is possible to uniformly dope the ions to the electrodes. However, in the pre-doping method described in Patent Document 1, since a metal foil having a plurality of through holes and a metallic lithium foil are used in the current collector, the manufacturing cost is high and the volumetric energy density of the power storage device is further lowered. There was also the problem of getting rid of it.

On the other hand, a pre-doping method that does not use a metallic lithium foil has also been proposed. For example, Patent Document 2 states that Li _a TiO _b (1.5 ≦ a ≦ 4.5, 2.7 ≦ b ≦ 4.8). A predoping agent for a lithium ion capacitor, which is characterized by containing the represented compound as a main component, is described. According to this, since lithium titanate having a specific composition is the main component, lithium ions required for predoping can be generated by a normal charging operation (aging), and a metallic lithium foil as before is used. It is said that pre-doping can be performed without any need. However, the pre-doping agent described in Patent Document 2 is premised on being blended with the positive electrode material, and in such a pre-doping method, the strength of the positive electrode is lowered and the film thickness of the positive electrode is increased to increase the resistance. There is a problem that the size becomes large and the performance of the power storage device deteriorates. Further, in Patent Document 2, a lithium metal composite oxide in which the molar ratio Li / Me of a specific metal element (Me) and a lithium metal satisfies a specific range, and the lithium metal composite oxide has an inverted fluorite-type structure. A pre-doping method capable of providing a power storage device having excellent rateability while maintaining electrode strength without any description or suggestion that the content of the pre-doping agent containing the lithium metal composite oxide satisfies a specific range. Was desired.

Patent No. 5220510 JP-A-2019-87590

The present invention has been made to solve the above problems, and it is possible to effectively perform predoping without adding a predoping agent to the electrode, and it is suitable as a power storage device having excellent rateability while maintaining electrode strength. It is an object of the present invention to provide a pre-doped sheet for a power storage device containing a lithium metal composite oxide having an inverted fluorite-type structure, which can be used in the above.

The above-mentioned problem is a pre-doped sheet for a power storage device containing a pre-doping agent containing a lithium metal composite oxide, and the lithium metal composite oxide is composed of lithium (Li) and a group consisting of Fe, Al, Mn and Co. It contains at least one selected metal element (Me), the lithium metal composite oxide has an inverted fluorite-type structure, and the Li / Me (molar ratio) of the lithium metal composite oxide is 3.0 <. By providing a pre-doping sheet for a power storage device, which satisfies Li / Me ≦ 7.5 and the content (X) of the ^{pre-doping agent is 0.3 <X <6.0 mg / cm 2.} It will be resolved.

At this time, in the X-ray diffraction measurement, the lithium metal composite oxide was 2θ (diffraction angle) = 23.7 ± 0.5 °, 33.6 ± 0.7 °, 36.5 ± 0.7 ° and It is preferable to have any diffraction peak intensity of 56.7 ± 0.5 °.

A separator for a power storage device containing the pre-doped sheet is a preferred embodiment, and a power storage device containing the pre-doped sheet is also a preferred embodiment.

The above object is a method for producing a pre-doped sheet for a power storage device containing a pre-doping agent containing a lithium metal composite oxide, and a coating material containing the pre-doping agent and an organic solvent is applied to the surface of a porous sheet base material. It is also solved by providing a method for producing a pre-doped sheet, which is characterized by the above.

Further, the above-mentioned problem is a method for producing a pre-doped sheet for a power storage device containing a pre-doping agent containing a lithium metal composite oxide, which comprises kneading the pre-doping agent with a resin to form the pre-doped sheet. It is also solved by providing a manufacturing method.

Further, the above-mentioned problem is a method for producing a pre-doped sheet for a power storage device containing a pre-doping agent containing a lithium metal composite oxide, and a coating material containing the pre-doping agent and an organic solvent is applied to the surface of a release film base material. It is also solved by providing a method for producing a pre-doped sheet, which is characterized by working.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a pre-doped sheet for a power storage device containing a lithium metal composite oxide having an inverted fluorite-type structure. By using the pre-doped sheet of the present invention, it is possible to effectively perform pre-doping without adding a pre-doping agent to the electrodes, so that a power storage device having excellent rateability while maintaining the electrode strength is preferably provided. ..

It is a figure which showed the state of the 90 ° bending test in an Example.

The pre-doped sheet for a power storage device of the present invention (hereinafter, may be abbreviated as "pre-doped sheet") contains a pre-doping agent containing a lithium metal composite oxide, and the lithium metal composite oxide is lithium. The lithium metal composite oxide contains (Li) and at least one metal element (Me) selected from the group consisting of Fe, Al, Mn and Co, and the lithium metal composite oxide has an inverted fluorite-type structure. The Li / Me (molar ratio) of the composite oxide satisfies 3.0 <Li / Me ≦ 7.5, and the content (X) of the predoping agent satisfies 0.3 <X <6.0 mg / cm ² . It is characterized by that.

As a result of diligent studies by the present inventors, it is a lithium metal composite oxide containing a specific metal element (Me) and in which the molar ratio Li / Me of the metal element (Me) and the lithium metal satisfies a specific range. , The lithium metal composite oxide has an inverted fluorite type structure, and the content of the predoping agent containing the lithium metal composite oxide satisfies a specific range, so that the power storage device has excellent rateability while maintaining the electrode strength. It was clarified that a pre-doped sheet for use was obtained. When a pre-doping agent is used, a technique is known in which a pre-doping agent is mixed in advance with an electrode and a voltage for initial charging is applied to pre-dope lithium ions. However, the present invention overturns such common general technical knowledge and conducts an electrode. It is possible to effectively pre-dope without blending with. As a result, it is possible to provide a power storage device having excellent rateability while maintaining the electrode strength as compared with the case where the pre-doping agent is blended in the electrode.

As is clear from the comparison between Examples and Comparative Examples described later, Comparative Example 1 and Comparative Example 1 obtained by using a predoping agent whose Li / Me (molar ratio) does not satisfy 3.0 <Li / Me ≦ 7.5. As a result of the 90 ° bending test of the pre-doped sheet of No. 2, it was confirmed that the surface coated with the pre-doping agent had peeled off and powder had fallen off. In Comparative Example 5 in which titanium (Ti) was used as the metal element (Me), as a result of the 90 ° bending test, the surface did not peel off or powder fell off, but the design of 1C was made in the production of a full cell (coin cell). The capacity realization rate was lowered, the predoping was insufficient, and the capacity retention rate of 10C with respect to 1C was also lowered (Comparative Example 16). Further, in Comparative Examples 6 to 14 in which the predoping agent was mixed with the positive electrode, as a result of the 90 ° bending test, peeling and powder falling of the surface occurred in most of the cases (Comparative Examples 7 to 14), and the surface of the surface was peeled off. Even in the case of Comparative Example 6 in which peeling and powder falling did not occur, the design capacity realization rate of 1C was lowered in the production of the full cell (coin cell), the predoping did not proceed well, and 10C with respect to 1C. The capacity retention rate was also reduced (Comparative Example 17). On the other hand, in the pre-doped sheets of Examples 1 to 12 obtained by using the pre-doping agent having a Li / Me (molar ratio) of 3.0 <Li / Me ≦ 7.5, the results of the 90 ° bending test were obtained. No peeling or powder falling off of the surface occurred, and in the production of a full cell (coin cell), the predoping progressed sufficiently because the design capacity realization rate of 1C was high, and the capacity retention rate of 10C with respect to 1C was also high. Was confirmed. Therefore, it is significant to adopt the above configuration, and the pre-doping sheet of the present invention enables effective pre-doping without mixing the pre-doping agent with the electrodes, so that the electrode strength is maintained and the rateability is excellent. A power storage device can be provided.

The lithium metal composite oxide used in the present invention contains lithium (Li) and at least one metal element (Me) selected from the group consisting of Fe, Al, Mn and Co, and Li / Me (molar ratio). ) Satisfies 3.0 <Li / Me ≦ 7.5 and has an inverted fluorite-type structure. Since the metal element (Me) is at least one selected from the group consisting of Fe, Al, Mn and Co, the lithium metal composite oxide containing lithium (Li) and the metal element (Me) is reversed. It will have a fluorite-shaped structure. Since the lithium metal composite oxide used in the present invention has an inverted fluorite-type structure in this way, lithium ions are easily desorbed, and after desorption, the crystal structure collapses and lithium ions are reinserted. Therefore, it is considered that the pre-doping effect is high. On the other hand, when the metal element (Me) is other than Fe, Al, Mn and Co, predoping may be insufficient. The metal element (Me) is preferably at least one selected from the group consisting of Fe, Al and Mn, and more preferably at least one selected from the group consisting of Fe and Mn.

The lithium metal composite oxide used in the present invention has 2θ (diffraction angle) = 23.7 ± 0.5 °, 33.6 ± 0.7 °, 36.5 ± 0.7 ° in X-ray diffraction measurement. And it is preferable to have a diffraction peak intensity of 56.7 ± 0.5 °. If it does not have any one of the diffraction peak intensities, the lithium metal composite oxide does not have a reverse fluorite type structure, the predoping becomes insufficient, and the capacity retention rate of 10C with respect to 1C may decrease. is there.

In the present invention, it is particularly important that the Li / Me (molar ratio) of the lithium metal composite oxide satisfies 3.0 <Li / Me ≦ 7.5. According to the study by the present inventors, among the lithium metal composite oxides having an inverted fluorite-type structure, Li / Me (molar ratio) is in a specific range, so that the storage capacity is excellent in rate while maintaining the electrode strength. It has been clarified that a pre-doped sheet suitable for use as a device can be provided. When Li / Me (molar ratio) is 3.0 or less, the strength of the pre-doped sheet may decrease and the film thickness may increase, and it is preferably 3.2 or more, preferably 3.5 or more. Is more preferable, 3.8 or more is more preferable, 4.2 or more is particularly preferable, and 4.5 or more is most preferable. On the other hand, when the Li / Me (molar ratio) exceeds 7.5, the strength of the pre-doped sheet may decrease and the rateability of the obtained power storage device may decrease, and it is preferably 7.3 or less. , 6.8 or less, more preferably 6.5 or less, and particularly preferably 6.2 or less.

The pre-doped sheet of the present invention needs to satisfy the content (X) of the pre-doping agent of 0.3 <X <6.0 mg / cm ^2. When the content (X) of the pre-doping agent is 0.3 mg / cm ² or less, the pre-doping may be insufficient and the design capacity realization rate may decrease. Therefore, it is preferably ^{0.35 mg / cm 2 or more, and 0.} More preferably, it is 4 mg / cm ^{2 or more.} On the other hand, when the content (X) of the predoping agent is 6.0 mg / cm ² or more, the electrode strength may decrease and the capacity retention rate may decrease, and the content is preferably ^{5.5 mg / cm 2 or less.} , more preferably 4.8 mg / cm ² or less, further preferably 3.5 mg / cm ² or less, particularly preferably at 2.8 mg / cm ² or less, 1.5 mg / cm ² or less Is most preferable.

The method for producing the predoping agent used in the present invention is not particularly limited. At least one metal raw material selected from the group consisting of a lithium raw material, an Fe raw material, an Al raw material, an Mn raw material, and a Co raw material is mixed (hereinafter, may be abbreviated as "mixing step") in an oxygen-free atmosphere. By firing (hereinafter, may be abbreviated as "firing step"), a predoping agent containing a lithium metal composite oxide can be obtained.

The lithium raw material is not particularly limited, and lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate, lithium oxide and the like are preferably used. These may be hydrates or anhydrides. Among them, lithium hydroxide is more preferably used.

The at least one metal raw material selected from the group consisting of the Fe raw material, the Al raw material, the Mn raw material, and the Co raw material is not particularly limited, but specifically, those exemplified below are preferably used. These may be hydrates or anhydrides. Examples of the Fe raw material include iron (II) oxide, iron (III) oxide, iron (II, III) oxide, iron (III) oxide hydroxide, ferrous sulfate (II), ferric sulfate (III), and the like. Examples thereof include iron (II) hydroxide and iron (III) hydroxide. Examples of the Al raw material include aluminum oxide, aluminum hydroxide, aluminum sulfate, aluminum nitrate and the like. Examples of the Mn raw material include manganese oxide, manganese hydroxide, manganese carbonate, manganese sulfate, manganese nitrate and the like. Examples of the Co raw material include cobalt oxide, cobalt hydroxide, cobalt sulfate, and cobalt nitrate.

In the mixing step, it is a preferable embodiment that a certain amount of carbon raw material is blended. The carbon raw material is not particularly limited, and polyvinyl alcohol, activated carbon, acetylene black, ketjen black, carbon nanotubes, carbon nanofibers, graphene and the like are preferably used. The blending amount of the carbon raw material is preferably 1 to 70 parts by weight with respect to 100 parts by weight of the total of the lithium raw material and the metal raw material. When the blending amount of the carbon raw material is less than 1 part by weight, the reaction between lithium and at least one metal element selected from the group consisting of Fe, Al, Mn and Co becomes non-uniform, and the obtained lithium metal composite oxidation is obtained. The material does not have an inverted fluorite-type structure, the predoping becomes insufficient, and the capacity retention rate of 10C with respect to 1C may decrease. The blending amount of the carbon raw material is more preferably 5 parts by weight or more, and further preferably 10 parts by weight or more. On the other hand, if the blending amount of the carbon raw material exceeds 70 parts by weight, the production cost becomes high, which is not preferable. The blending amount of the carbon raw material is more preferably 60 parts by weight or less, and further preferably 50 parts by weight or less.

In the mixing step, the lithium raw material and the metal raw material are mixed, and preferably the carbon raw material is also mixed. It may be mixed by a dry method or a wet method, but it is preferable to pulverize the mixture when mixing. When crushing, a crushing device such as a ball mill, a planetary mill, a raikai machine, a jet mill, or a pin mill is preferably used.

In the firing step, it is preferable to fire in an oxygen-free atmosphere, for example, an inert gas atmosphere, a hydrogen gas atmosphere, or a hydrogen-inert gas atmosphere, and nitrogen, argon, helium, neon, krypton, etc. are used as the inert gas. It is preferably used. Further, the firing temperature in the firing step is preferably 650 to 1000 ° C. When the calcination temperature is less than 650 ° C., the unreacted raw material remains, the obtained lithium metal composite oxide does not have a reverse fluorite type structure, the predoping becomes insufficient, and the capacity retention rate of 10C with respect to 1C is also high. It may decrease. The firing temperature is more preferably 750 ° C. or higher, and even more preferably 850 ° C. or higher. If the calcination temperature exceeds 1000 ° C., it becomes difficult to pulverize the obtained lithium metal composite oxide, the particles after pulverization become coarse, and the production of a pre-doped sheet may become difficult. The firing temperature is more preferably 980 ° C. or lower.

The firing time in the firing step is preferably 2 to 80 hours. If the calcination time is less than 2 hours, the unreacted raw material remains, the obtained lithium metal composite oxide does not have a reverse fluorite type structure, the predoping is insufficient, and the capacity retention rate of 10C with respect to 1C is also high. It may decrease. The firing time is more preferably 10 hours or more, further preferably 24 hours or more, and particularly preferably 48 hours or more. On the other hand, if the firing time exceeds 80 hours, the productivity may decrease. The firing time is more preferably 75 hours or less.

A pre-doped sheet can be obtained by using the lithium metal composite oxide obtained as described above as a pre-doping agent and forming it into a sheet. The method for producing the pre-doped sheet of the present invention is not particularly limited, but (1) the pre-doped sheet is produced by applying a coating material containing the pre-doping agent and an organic solvent to the surface of the porous sheet base material (1). Hereinafter, "manufacturing method 1" may be abbreviated) is a preferred embodiment, and (2) a pre-doped sheet is produced by kneading the resin with the pre-doping agent and molding the resin (hereinafter, "manufacturing"). Method 2 ”) is also a preferred embodiment. Further, (3) a pre-doped sheet is produced by applying a coating material containing the pre-doping agent and an organic solvent on the surface of the release film base material (hereinafter, may be abbreviated as "Production Method 3"). Is also a preferred embodiment.

The porous sheet base material used in the production method 1 is not particularly limited as long as it is a base material that can be formed into a sheet shape by applying a paint containing the predoping agent and an organic solvent, but the film, woven fabric, and the like. Nonwoven fabrics are preferably used. Materials include polypropylene, polybutene, polyhexene, ethylene polyfluoride, polyvinyl chloride, polyvinyl acetate, acetalized polyvinyl alcohol, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-methylbutene copolymer, ethylene-methyl. Examples thereof include a penten copolymer and an ethylene tetrafluoride / propylene hexafluoride copolymer.

The organic solvent used is not particularly limited, and N-methyl-2-pyrrolidone or the like is preferably used, and the viscosity of the coating material can be adjusted. In addition to the predoping agent and the organic solvent, the paint also contains natural graphite (scaly graphite, scaly graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, and carbon as conductive aids. Examples thereof include an embodiment containing a conductive material such as a fiber, a metal (copper, nickel, aluminum, silver, etc.) powder or a fiber, a polyphenylene derivative, or a mixture thereof. In addition, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-dienter polymer (EPDM), sulfonated EPDM, styrene butadiene rubber, polybutadiene, etc. An embodiment in which fluororubber, polyethylene oxide, or the like is contained as one type or a mixture thereof can also be mentioned. In the coating of the paint, the coating amount can be suitably adjusted by using a bar coater, a knife coater, a roll coater, or the like. In this way, the pre-doped sheet of the present invention can be preferably obtained. The coating pattern on the porous sheet base material is not particularly limited, and the coating may be applied to the entire surface of the sheet, but it may be partially striped, frame-shaped, disk-shaped, lattice-shaped, or dot-shaped. Overlapping is also preferably used. The stacking interval is preferably constant, but does not have to be constant.

The resin used in the production method 2 is not particularly limited, and polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; and resins such as polyamide such as nylon are preferably used. These resins may be monomers or copolymers. The pre-doped sheet of the present invention can be suitably obtained by kneading the resin and the pre-doping agent and molding the resin into a sheet by a doctor blade method, pressing, or stretching.

The release film base material used in the production method 3 is not particularly limited as long as it is a base material that can be formed into a sheet by applying a paint containing the predoping agent and an organic solvent, but is not particularly limited. , Non-silicone type release film is preferably used. Materials include polypropylene, polybutene, polyhexene, ethylene polyfluoride, polyvinyl chloride, polyvinyl acetate, acetalized polyvinyl alcohol, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-methylbutene copolymer, ethylene-methyl. Examples thereof include penten copolymers, ethylene tetrafluoride / propylene hexafluoride copolymers, and polyethylene terephthalates.

The organic solvent used is not particularly limited, and N-methyl-2-pyrrolidone or the like is preferably used, and the viscosity of the coating material can be adjusted. In addition to the predoping agent and the organic solvent, the paint also contains natural graphite (scaly graphite, scaly graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, and carbon as conductive aids. Examples thereof include an embodiment containing a conductive material such as a fiber, a metal (copper, nickel, aluminum, silver, etc.) powder or a fiber, a polyphenylene derivative, or a mixture thereof. In addition, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-dienter polymer (EPDM), sulfonated EPDM, styrene butadiene rubber, polybutadiene, etc. An embodiment in which fluororubber, polyethylene oxide, silicone rubber and the like are contained as one kind or a mixture thereof can also be mentioned. In the coating of the paint, the coating amount can be suitably adjusted by using a bar coater, a knife coater, a roll coater, or the like. In this way, the pre-doped sheet of the present invention can be preferably obtained. The coating pattern on the release film base material is not particularly limited and may be applied to the entire surface of the sheet, but it may be partially striped, frame-shaped, disk-shaped, lattice-shaped, or dot-shaped. Overlapping is also preferably used. The stacking interval is preferably constant, but does not have to be constant.

The pre-doped sheet thus obtained is preferably arranged so as to be in contact with the positive electrode from the viewpoint of effectively performing pre-doping. At this time, the pre-doped sheet may be arranged so as to be in contact with the surface of the positive electrode, or the pre-doped sheet may be arranged so as to be in contact with the back surface of the positive electrode. Further, it is also preferable that the pre-doped sheet is arranged between the positive electrode and the negative electrode, and in particular, after the pre-doped treatment is performed by applying the voltage of the initial charge, the pre-doped sheet can serve as an insulator and thus functions as a separator. It became clear by the present inventors. From this point of view, a separator for a power storage device including a pre-doped sheet is a preferred embodiment.

As described above, the pre-doping sheet of the present invention can effectively pre-dope without blending the pre-doping agent in the electrode, and maintains the electrode strength as compared with the case where the pre-doping agent is blended in the electrode. It has an excellent rate effect. Therefore, a power storage device including a pre-doped sheet is a preferred embodiment. The power storage device is not particularly limited, and at least one power storage device selected from the group consisting of a lithium ion battery, a lithium ion capacitor, and an electric double layer capacitor is suitable.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Preparation of pre-doping agent]
Examples of preparation of the lithium metal composite oxide used as the predoping agent are shown in Samples 1 to 7 and

Comparative Samples

1 and 2. Each sample was handled in an environment where the influence of atmospheric humidity was small.
[X-ray diffraction measurement]
Common to materials with inverted fluorite structure, 2θ (diffraction angle) = 23.7 ± 0.5 °, 33.6 ± 0.7 °, 36.5 ± 0.7 °, 56.7 ± Clear peaks appear at 0.5 °. X-ray diffraction measurements were performed on the obtained samples 1 to 7 and

comparative samples

1 and 2, respectively. For X-ray diffraction measurement, use the XRD device "X'pert-PRO" manufactured by Philips Co., Ltd. to measure each sample prepared with Cu Kα rays, and only if a peak exists at the corresponding position, the peak position. Is shown in Table 1.

(Sample 1: Li / Fe = 4.9)
Weigh iron oxide (manufactured by Aldrich, Fe ₃ O ₄ ) and lithium hydroxide monohydrate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) so that Li: Fe = 5.0: 1 in terms of molar ratio. Further, the same weight of polyvinyl alcohol (manufactured by Aldrich) was charged into the planetary ball mill with respect to the total amount, and pulverized and mixed for 9 hours. The mixture was taken out and calcined in a box-shaped electric furnace at 950 ° C. for 72 hours in a nitrogen atmosphere of 2 L / min. A sample that is a predoping agent containing a lithium metal composite oxide (Li / Fe = 4.9) whose metal type is Fe by crushing the fired product with a hammer mill and then removing coarse particles with a sieve having a mesh size of 100 μm. I got 1.

[ICP measurement]
By adding 10 mL of sulfuric acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., for 98% precision analysis) to 0.05 g of the above sample 1 (pre-doping agent), and dropping water while heating with a heater at 200 ° C. , Completely dissolved. The concentration of lithium and the metal species in the obtained pre-doping agent sulfuric acid solution was calculated to be about 1 to 2 ppm, and the solution was prepared by diluting with water. The prepared solution was measured using an ICP emission spectrophotometer (SPECTRO RACOS EOP). From the measurement result of ICP, the content of Li contained in Sample 1 was 22 wt%, and Li / Fe was 4.9. The measurement results are shown in Table 1.

(Sample 2: Li / Fe = 7.2)
Lithium metal composite oxide (Li / Fe =) whose metal type is Fe in the same manner as in Sample 1 except that iron oxide and lithium hydroxide monohydrate are converted into Li: Fe = 7.4: 1 in terms of molar ratio. Sample 2 was obtained as a predoping agent containing 7.2). When the concentration of the sulfuric acid solution of the obtained sample 2 was diluted to the same concentration as that of the sample 1 and measured by ICP, the content of Li contained in the predoping agent of the sample 2 was 28 wt%, and the Li / Fe was 7.2. It was. The measurement results are shown in Table 1.

(Sample 3: Li / Fe = 7.8)
Lithium metal composite oxide (Li / Fe =) whose metal type is Fe in the same manner as in Sample 1 except that iron oxide and lithium hydroxide monohydrate are converted into Li: Fe = 8.0: 1 in terms of molar ratio. Sample 3 was obtained as a predoping agent containing 7.8). When the concentration of the sulfuric acid solution of the obtained sample 3 was diluted to the same concentration as that of the sample 1 and measured by ICP, the content of Li contained in the predoping agent of the sample 3 was 29 wt%, and the Li / Fe was 7.8. It was. The measurement results are shown in Table 1.

(Sample 4: Li / Fe = 2.2)
Lithium metal composite oxide (Li / Fe =) whose metal type is Fe in the same manner as in Sample 1 except that iron oxide and lithium hydroxide monohydrate are converted to Li: Fe = 2.4: 1 in terms of molar ratio. Sample 4 was obtained as a predoping agent containing 2.2). When the concentration of the sulfuric acid solution of the obtained sample 4 was diluted to the same concentration as that of the sample 1 and measured by ICP, the content of Li contained in the predoping agent of the sample 4 was 9 wt%, and the Li / Fe was 2.2. It was. The measurement results are shown in Table 1.

(Sample 5: Li / Mn = 5.9)
_{Manganese oxide (MnO 2} manufactured by Aldrich) is used instead of iron oxide, and manganese oxide and lithium hydroxide monohydrate are converted into Li: Mn = 6: 1 in terms of molar ratio in the same manner as in Sample 1. Sample 5 was obtained as a predoping agent containing a lithium metal composite oxide (Li / Mn = 5.9) having a metal type of Mn. When the concentration of the sulfuric acid solution of the obtained sample 5 was diluted to the same concentration as that of the sample 1 and measured by ICP, the content of Li contained in the predoping agent of the sample 5 was 24 wt%, and the Li / Mn was 5.9. It was. The measurement results are shown in Table 1.

(Sample 6: Li / Co = 5.8)
Cobalt oxide (made by Aldrich, CoO) is used instead of iron oxide, and the same as in sample 1 except that cobalt oxide and lithium hydroxide monohydrate are converted to Li: Co = 6.0: 1 in terms of molar ratio. Then, Sample 6 was obtained as a predoping agent containing a lithium metal composite oxide (Li / Co = 5.8) having a metal type of Co. When the concentration of the sulfuric acid solution of the obtained sample 6 was diluted to the same concentration as that of the sample 1 and measured by ICP, the content of Li contained in the predoping agent of the sample 6 was 24 wt%, and the Li / Co was 5.8. It was. The measurement results are shown in Table 1.

(Sample 7: Li / Al = 4.9)
Sample 1 except that aluminum oxide (made by Aldrich, Al ₂ O ₃ ) is used instead of iron oxide, and aluminum oxide and lithium hydroxide monohydrate are converted into Li: Al = 5.0: 1 in terms of molar ratio. In the same manner as above, Sample 7 was obtained as a predoping agent containing a lithium metal composite oxide (Li / Al = 4.9) having a metal type of Al. When the concentration of the sulfuric acid solution of the obtained sample 7 was diluted to the same concentration as that of the sample 1 and measured by ICP, the content of Li contained in the predoping agent of the sample 7 was 18 wt%, and the Li / Al was 4.9. It was. The measurement results are shown in Table 1.

(Comparative sample 1)
Weigh iron oxide (manufactured by Aldrich, Fe ₃ O ₄ ) and lithium hydroxide monohydrate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) so that Li: Fe = 5.0: 1 in terms of molar ratio. Comparative sample 1 was obtained by throwing it into a planetary ball mill, pulverizing and mixing for 9 hours. When the concentration of the sulfuric acid solution of the obtained comparative sample 1 was diluted to the same concentration as that of the sample 1 and measured by ICP, the content of Li contained in the predoping agent of the comparative sample 1 was 12 wt%, and Li / Fe was 5.0. Met. The measurement results are shown in Table 1.

(Comparative sample 2)
Anatase-type titanium oxide (Tio ₂ manufactured by Aldrich) is used instead of iron oxide, and anatase-type titanium oxide and lithium hydroxide monohydrate are converted into a molar ratio of Li: Ti = 4.0: 1. Comparative sample 2 was obtained in the same manner as in sample 1 except that. When the concentration of the sulfuric acid solution of the obtained comparative sample 2 was diluted to the same concentration as that of the sample 1 and measured by ICP, the content of Li contained in the predoping agent of the comparative sample 2 was 20 wt%, and Li / Ti was 4.0. Met. The measurement results are shown in Table 1.

[Preparation and evaluation of pre-doped sheet]
(Example 1)
Sample 1 is used as the pre-doping agent, and acetylene black (Denka Black, manufactured by Denka Corporation) is used as the conductive auxiliary agent, and polyvinylidene fluoride (Kureha Corporation, KF polymer # 9130), which is a binder, is added to these to rotate and rotate. A paint was obtained by kneading with a revolution mixer and adjusting the viscosity with N-methyl-2-pyrrolidone (NMP). The mass ratio of the pre-doping agent / conductive auxiliary agent / binder was 85/5/10. Subsequently, the produced paint is applied to a cellulose-based non-woven fabric (manufactured by Nippon Kodoshi Kogyo Co., Ltd., TF40), which is a porous sheet base material, using a bar coater, and punched to a size of φ16 to form a pre-doped sheet. Obtained.

[Evaluation of pre-doping agent amount and electric capacity (Li amount)]
From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 0.5 mg / cm ² , and the amount of Li present on the pre-doped sheet was calculated by the following, and it was found to be 0.9 mAh. The existence of Li was confirmed. The calculation method is shown below.
Electrode weight-Base material weight = Solid content weight Solid content weight x Pre-doping agent% = Pre-doping agent weight Pre-doping agent weight x Lithium content (measured from ICP) = Lithium weight Lithium weight ÷ Lithium molecular weight = Lithium molar number Here from the Faraday constant ,
96485C / mol = 26.801mAh / mmol
Lithium mole number x 26.801 mAh / mmol = electric capacity mAh (Li amount)

[90 ° bending test]
A pre-doped sheet cut to a width of about 5 cm × 10 cm was held by hand at both ends so that the coated surface was facing upward, and pressed against a cylindrical iron rod having a diameter of 1 cm. The pre-doped sheet or the electrode was bent to 90 ° with the portion touching the rod as the apex, and the peeling of the coated surface was visually confirmed (see FIG. 1). In addition, during the test, powder removal was confirmed by laying a blank sheet underneath. Table 2 shows those in which peeling or powder falling was confirmed as B, and those in which no peeling or powder was confirmed as A. When the pre-doped sheet obtained in Example 1 was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 2)
In Example 1, a pre-doped sheet was obtained in the same manner as in Example 1 except that Sample 2 was used as a pre-doping agent instead of Sample 1. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 0.5 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, it was found to be 1.1 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 3)
In Example 1, a pre-doped sheet was obtained in the same manner as in Example 1 except that the amount of paint applied to the porous sheet base material was changed by changing the bar coater used. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 0.7 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, it was found to be 1.2 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 4)
In Example 1, a pre-doped sheet was obtained in the same manner as in Example 1 except that the amount of paint applied to the porous sheet base material was changed by changing the bar coater used. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 2.7 mg / cm ² , and the amount of Li present on the pre-doped sheet was calculated to be 4.6 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 5)
In Example 1, a pre-doped sheet was obtained in the same manner as in Example 1 except that the amount of paint applied to the porous sheet base material was changed by changing the bar coater used. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 4.7 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, it was 8.1 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 6)
In Example 1, a pre-doped sheet was obtained in the same manner as in Example 1 except that the amount of paint applied to the porous sheet base material was changed by changing the bar coater used. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 0.4 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, it was found to be 0.7 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 7)
A pre-doped sheet was obtained in the same manner as in Example 1 except that the porous sheet base material used was changed to a polyester-based non-woven fabric (Japan Vilene). From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 0.5 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, it was found to be 0.8 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 8)
A pre-doped sheet was obtained in the same manner as in Example 1 except that the porous sheet base material used was changed to a polyolefin film (Asahi Kasei, hypoa separator). From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 0.5 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, it was found to be 0.8 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 9)
In Example 1, a pre-doped sheet was obtained in the same manner as in Example 1 except that Sample 5 was used as a pre-doping agent instead of Sample 1. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 0.5 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, it was 1.0 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 10)
In Example 1, a pre-doped sheet was obtained in the same manner as in Example 1 except that Sample 6 was used as the pre-doping agent instead of Sample 1. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 0.5 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, it was found to be 0.9 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 11)
In Example 1, a pre-doped sheet was obtained in the same manner as in Example 1 except that Sample 7 was used as a pre-doping agent instead of Sample 1. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 0.6 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, it was found to be 1.3 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 12)
After adding 1 g of Sample 1 to 5 g of a 5 wt% toluene solution of granular polyethylene (NUC, EVA COPOLYMER), the mixture was kneaded at 40 ° C. using a rotation / revolution mixer. The obtained mixture was coated on a glass plate using the doctor blade method, dried by hot air from a dryer, and then peeled off from the edges to obtain a film-shaped pre-doped sheet. The amount of pre-doping agent (coating amount) and the amount of Li were calculated by measuring the obtained film as it was with ICP, the amount of pre-doping agent was 0.6 mg / cm ² , and the presence of Li of 1.0 mAh was present. It was confirmed. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 13)
Sample 1 is used as the pre-doping agent, and acetylene black (Denka Black, manufactured by Denka Corporation) is used as the conductive auxiliary agent, and polyvinylidene fluoride (Kureha Corporation, KF polymer # 9130), which is a binder, is added to these to rotate and rotate. A paint was obtained by kneading with a revolution mixer and adjusting the viscosity with N-methyl-2-pyrrolidone (NMP). The mass ratio of the pre-doping agent / conductive auxiliary agent / binder was 95/2/3. Subsequently, the produced paint is applied to a silicone type release film (HY-S30-2, manufactured by Higashiyama Film Co., Ltd.), which is a release film base material, using a bar coater and punched to a size of φ16. A pre-doped sheet was obtained. The amount of pre-doping agent (coating amount) and the amount of Li were calculated by measuring the obtained film as it was with ICP, the amount of pre-doping agent was 0.5 mg / cm ² , and the presence of Li of 0.9 mAh was present. It was confirmed. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 14)
A pre-doped sheet was obtained in the same manner as in Example 13 except that the amount of the paint applied was changed in Example 13. The amount of pre-doping agent (coating amount) and the amount of Li were calculated by measuring the obtained film as it was with ICP, and the amount of pre-doping agent was 2.7 mg / cm ² and the presence of Li for 4.6 mAh. It was confirmed. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Example 15)
A pre-doped sheet was obtained in the same manner as in Example 13 except that the amount of the paint applied was changed in Example 13. The amount of pre-doping agent (coating amount) and the amount of Li were calculated by measuring the obtained film as it was with ICP, and the amount of pre-doping agent was 4.7 mg / cm ² and the presence of Li for 8.1 mAh. It was confirmed. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Comparative Example 1)
In Example 1, the same as in Example 1 except that sample 4 was used as a pre-doping agent instead of sample 1 and the amount of paint applied to the porous sheet substrate was changed by changing the bar coater used. To obtain a pre-doped sheet. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 6.6 mg / cm ² , and the amount of Li present on the pre-doped sheet was calculated to be 4.6 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, it was confirmed that the coated surface was peeled off. The results are shown in Table 2.

(Comparative Example 2)
In Example 1, the same as in Example 1 except that sample 3 was used as a pre-doping agent instead of sample 1 and the amount of paint applied to the porous sheet substrate was changed by changing the bar coater used. To obtain a pre-doped sheet. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 2.0 mg / cm ² , and the amount of Li present on the pre-doped sheet was calculated to be 4.6 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, it was confirmed that the coated surface was peeled off and powder was removed. The results are shown in Table 2.

(Comparative Example 3)
In Example 1, a pre-doped sheet was obtained in the same manner as in Example 1 except that the amount of paint applied to the porous sheet base material was changed by changing the bar coater used. The amount of predoping agent (coating amount) was 6.0 mg / cm ² from the weight of the obtained predope sheet, and when the amount of Li present on the predope sheet was calculated, the presence of Li of 10.2 mAh was calculated. It was confirmed. When the obtained pre-doped sheet was subjected to a 90 ° bending test, powder falling occurred. The results are shown in Table 2.

(Comparative Example 4)
In Example 1, the comparative sample 1 was used as the pre-doping agent instead of the sample 1, and the amount of the paint applied to the porous sheet base material was changed by changing the bar coater used. Similarly, a pre-doped sheet was obtained. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 2.6 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, 1.2 mAh of Li was calculated. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

(Comparative Example 5)
In Example 1, the comparative sample 2 was used as the pre-doping agent instead of the sample 1, and the amount of the paint applied to the porous sheet base material was changed by changing the bar coater used. Similarly, a pre-doped sheet was obtained. From the weight of the obtained pre-doped sheet, the amount of pre-doping agent (coating amount) was 1.4 mg / cm ² , and when the amount of Li present on the pre-doped sheet was calculated, it was found to be 1.1 mAh of Li. Confirmed existence. When the obtained pre-doped sheet was subjected to a 90 ° bending test, no peeling or powder falling occurred. The results are shown in Table 2.

[Preparation and evaluation of pre-doped positive electrode]
(Comparative Example 6)
Sample 1 was used as the pre-doping agent, activated charcoal (Kureha Corporation, YP50F) was used as the positive electrode active material, and acetylene black (Denka Black Co., Ltd., Denka Black) was used as the conductive auxiliary agent. In addition to KF polymer # 9130) manufactured by Kureha Corporation, the mixture was kneaded using a rotation / revolution mixer, and the viscosity was adjusted with N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode paint. The mass ratio of the pre-doping agent / positive electrode active material / conductive auxiliary agent / binder was 7/70/9/14. Subsequently, the prepared positive electrode paint was coated on one side of an etched aluminum foil (manufactured by Nippon Denki Kogyo Co., Ltd., JCC-20CB), which is a current collector, dried at 130 ° C. for 30 minutes, and then with a slit of 0.01 mm. A pre-doped agent mixed positive electrode was prepared by roll pressing. At this time, the theoretical capacity of activated carbon was calculated at 40 mAh / g, and the coating film thickness was adjusted so that 0.2 mAh of activated carbon was applied when punched with a φ15 punch. From the weight of the obtained pre-doping agent mixed positive electrode, the amount of pre-doping agent (coating amount) was 0.2 mg / cm ² , and it was estimated that 0.4 mAh of Li was present. When a 90 ° bending test was performed on the pre-doped agent mixed positive electrode, no peeling or powder falling occurred. The results are shown in Table 3.

(Comparative Example 7)
In Comparative Example 6, the pre-doped agent mixed positive electrode was prepared in the same manner as in Comparative Example 6 except that the mass ratio of the pre-doping agent / positive electrode active material / conductive auxiliary agent / binder was set to 8/69/9/14. Obtained. From the weight of the obtained pre-doping agent mixed positive electrode, the amount of pre-doping agent (coating amount) was 0.3 mg / cm ² , and it was estimated that 0.5 mAh of Li was present. When a 90 ° bending test was performed on the pre-doped agent mixed positive electrode, it was confirmed that the coated surface was peeled off. The results are shown in Table 3.

(Comparative Example 8)
In Comparative Example 6, the pre-doped agent mixed positive electrode was prepared in the same manner as in Comparative Example 6 except that the mass ratio of the pre-doping agent / positive electrode active material / conductive auxiliary agent / binder was 11/66/9/14. Obtained. From the weight of the obtained pre-doping agent mixed positive electrode, the amount of pre-doping agent (coating amount) was 0.4 mg / cm ² , and it was estimated that 0.7 mAh of Li was present. When a 90 ° bending test was performed on the pre-doped agent mixed positive electrode, it was confirmed that the coated surface was peeled off and powder was removed. The results are shown in Table 3.

(Comparative Example 9)
In Comparative Example 6, the pre-doped agent mixed positive electrode was prepared in the same manner as in Comparative Example 6 except that the mass ratio of the pre-doping agent / positive electrode active material / conductive auxiliary agent / binder was 17/60/9/14. Obtained. From the weight of the obtained pre-doping agent mixed positive electrode, the amount of pre-doping agent (coating amount) was 0.7 mg / cm ² , and it was estimated that 1.2 mAh of Li was present. Since the surface of the obtained pre-doped mixed positive electrode was peeled off at the time of pressing, the 90 ° bending test was not performed. The results are shown in Table 3.

(Comparative Example 10)
In Comparative Example 6, a pre-doping agent mixed positive electrode was obtained in the same manner as in Comparative Example 6 except that Sample 3 was used as the pre-doping agent instead of Sample 1. From the weight of the obtained pre-doping agent mixed positive electrode, the amount of pre-doping agent (coating amount) was 0.2 mg / cm ² , and it was estimated that 0.5 mAh of Li was present. When a 90 ° bending test was performed on the pre-doped agent mixed positive electrode, it was confirmed that the coated surface was peeled off. The results are shown in Table 3.

(Comparative Example 11)
Sample 1 was used as the pre-doping agent, activated carbon (manufactured by Kuraray Co., Ltd., YP50F) was used as the positive electrode active material, and acetylene black (manufactured by Denka Co., Ltd., Denka Black) was used as the conductive auxiliary agent. It was added to a 1% by mass aqueous solution of H-1496B manufactured by Kogyo Seiyaku Co., Ltd. and kneaded using a rotation / revolution mixer to obtain a kneaded product. Next, a styrene-butadiene rubber (manufactured by JSR Corporation) as a binder was added to the prepared kneaded product to prepare a paint for a positive electrode, and the viscosity was adjusted with water. The mass ratio of the pre-doping agent / positive electrode active material / conductive auxiliary agent / thickener / binder was 9/73/9/4/5. When the obtained positive electrode paint was applied to an Al current collector, Al corroded and hydrogen gas was generated. The pre-doped agent-mixed positive electrode obtained by drying had irregularities on the electrode surface due to the influence of generated bubbles. From the weight of the obtained pre-doping agent mixed positive electrode, the amount of pre-doping agent (coating amount) was 0.6 mg / cm ² , and it was estimated that 0.4 mAh of Li was present. In addition, the 90 ° bending test was not performed because the coated surface was peeled off when the press was applied.

(Comparative Example 12)
In Comparative Example 7, a pre-doping agent mixed positive electrode was obtained in the same manner as in Comparative Example 7 except that Sample 5 was used as the pre-doping agent instead of Sample 1. From the weight of the obtained pre-doping agent mixed positive electrode, the amount of pre-doping agent (coating amount) was 0.3 mg / cm ² , and it was estimated that 0.4 mAh of Li was present. When a 90 ° bending test was performed on the pre-doped agent mixed positive electrode, it was confirmed that the coated surface was peeled off. The results are shown in Table 3.

(Comparative Example 13)
In Comparative Example 7, a pre-doping agent mixed positive electrode was obtained in the same manner as in Comparative Example 7 except that Sample 6 was used as the pre-doping agent instead of Sample 1. From the weight of the obtained pre-doping agent mixed positive electrode, the amount of pre-doping agent (coating amount) was 0.3 mg / cm ² , and it was estimated that 0.4 mAh of Li was present. When a 90 ° bending test was performed on the pre-doped agent mixed positive electrode, it was confirmed that the coated surface was peeled off. The results are shown in Table 3.

(Comparative Example 14)
In Comparative Example 7, a pre-doping agent mixed positive electrode was obtained in the same manner as in Comparative Example 7 except that Sample 7 was used as the pre-doping agent instead of Sample 1. From the weight of the obtained pre-doping agent mixed positive electrode, the amount of pre-doping agent (coating amount) was 0.3 mg / cm ² , and it was estimated that 0.3 mAh of Li was present. When a 90 ° bending test was performed on the pre-doped agent mixed positive electrode, it was confirmed that the coated surface was peeled off. The results are shown in Table 3.

[Making and evaluation of full cell (coin cell)]
(Example 16)
A full cell was prepared using the pre-doped sheet prepared in Example 3 as a separator, and a charge / discharge test was performed. The manufacturing method and the evaluation method are shown below.

(1) Preparation of negative electrode First, graphite (manufactured by Nippon Graphite Industry Co., Ltd., CGB-20) is used as the negative electrode active material, and acetylene black (manufactured by Denka Co., Ltd., Denka Black) is used as a conductive auxiliary agent, and these are used as a thickener. A 1% by mass aqueous solution of a certain carboxymethyl cellulose (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., H-1496B) was added and kneaded using a rotation / revolution mixer to obtain a kneaded product, and the viscosity was adjusted with water. Next, styrene-butadiene rubber (manufactured by JSR) as a binder was added to the prepared kneaded product, and the mixture was further kneaded using a rotation / revolution mixer to prepare a paint for a negative electrode. The mass ratio of the negative electrode active material / conductive auxiliary agent / thickener / binder was 95/1/1/3. Finally, the prepared negative electrode paint is applied to a copper foil (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.), which is a current collector, on one side, dried at 100 ° C. for 30 minutes, and then roll-pressed with a 0.01 mm slit. By doing so, a negative electrode was produced.

(2) Preparation of positive electrode Activated carbon (manufactured by Kuraray Co., Ltd., YP-50F) is used as the positive electrode active material, and acetylene black (manufactured by Denka Co., Ltd., Denka Black) is used as a conductive auxiliary agent, and polyvinylidene fluoride, which is a binder, is used as a binder. In addition to (KF Polymer # 9130, manufactured by Kureha Co., Ltd.), the mixture was kneaded using a rotation / revolution mixer, and the viscosity was adjusted with N-methyl-2-pyrrolidone to prepare a positive electrode paint. The mass ratio of the positive electrode active material / conductive auxiliary agent / binder was 77/9/14. Subsequently, the prepared positive electrode paint was coated on one side of an etched aluminum foil (manufactured by Nippon Denki Kogyo Co., Ltd., JCC-20CB), which is a current collector, dried at 130 ° C. for 30 minutes, and then with a slit of 0.01 mm. A positive electrode was produced by roll pressing. At this time, the theoretical capacity of activated carbon was calculated at 40 mAh / g, and the coating film thickness was adjusted so that 0.2 mAh of activated carbon was applied when punched with a φ15 punch.

(3) Cell design Since the capacity of the positive electrode produced above is 0.2 mAh, the negative electrode having a capacity ratio of N (negative electrode active material) / P (positive electrode active material) approaching 10, that is, 2.0 mAh. A negative electrode coated with graphite was used.

(4) Cell Preparation The pre-doped sheet produced in Example 3 was punched to a size of φ16, the coated surface of the pre-doping agent was arranged so as to face the surface of the positive electrode, and the negative electrode was placed on the separator. On the other hand, a 2032 type coin cell was prepared by using an electrolytic solution in _{which 1 mol of LiBF 4} was added as an electrolyte to 1 L of a PC (propylene carbonate) solvent (1.0 M LiBF _{4 / PC).} The total film thickness of the positive electrode and the separator at this time was 129 μm.

(5) Charge / discharge test A pre-doping operation was performed using the produced coin cell. Specifically, the battery was charged to 4.5 V at a rate of 0.1 C based on activated carbon, and then the potential was maintained for 24 hours by a constant voltage operation. After that, it was discharged to 2.2 V at 1 C, operated for 3 cycles at 1 C for 3.8-2.2 V, and then charged / discharged at 10 C for 3 cycles. As a result of the charge / discharge test, the discharge capacity in the third cycle was 0.19 mAh at 1C and 0.15 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 95% at 1C and 75% at 10C. The results are shown in Table 4. A 3-minute rest was performed between each charge and discharge. The measurement was performed using HJ1001SD8 manufactured by Hokuto Denko Co., Ltd.

(Example 17)
In Example 16, a coin cell was prepared and a charge / discharge test was carried out in the same manner as in Example 16 except that the pre-doped sheet prepared in Example 5 was used as a separator. The total film thickness of the positive electrode and the separator at this time was 140 μm. As a result, the discharge capacity in the third cycle was 0.22 mAh at 1C and 0.14 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 110% at 1C and 70% at 10C. The results are shown in Table 4.

(Example 18)
In Example 16, a coin cell was prepared and a charge / discharge test was carried out in the same manner as in Example 16 except that the pre-doped sheet prepared in Example 6 was used as a separator. The total film thickness of the positive electrode and the separator at this time was 123 μm. As a result, the discharge capacity in the third cycle was 0.15 mAh at 1C and 0.12 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 75% at 1C and 60% at 10C. The results are shown in Table 4.

(Example 19)
In Example 16, the same as in Example 16 except that the pre-doped sheet prepared in Example 12 was placed between the positive electrode and the separator, and a cellulosic non-woven fabric (manufactured by Nippon Kodoshi Kogyo Co., Ltd., TF40) was used as the separator. Then, a coin cell was prepared and a charge / discharge test was performed. The total film thickness of the positive electrode, the separator, and the pre-doped sheet at this time was 128 μm. As a result, the discharge capacity in the third cycle was 0.19 mAh at 1C and 0.12 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 95% at 1C and 60% at 10C. The results are shown in Table 4.

(Example 20)
In Example 16, the same as in Example 16 except that the pre-doped sheet prepared in Example 3 was placed on the back surface of the positive electrode and a cellulosic non-woven fabric (manufactured by Nippon Kodoshi Kogyo Co., Ltd., TF40) was used as a separator. , A coin cell was prepared and a charge / discharge test was performed. The total film thickness of the pre-doped sheet, the positive electrode, and the separator at this time was 149 μm. As a result, the discharge capacity in the third cycle was 0.20 mAh at 1C and 0.16 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 100% at 1C and 80% at 10C. The results are shown in Table 4.

(Example 21)
In Example 16, a coin cell was prepared and a charge / discharge test was carried out in the same manner as in Example 16 except that the pre-doped sheet prepared in Example 9 was used. The total film thickness of the positive electrode and the separator at this time was 127 μm. As a result, the discharge capacity in the third cycle was 0.19 mAh at 1C and 0.15 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 95% at 1C and 75% at 10C. The results are shown in Table 4.

(Example 22)
In Example 16, the coin cell was prepared and coin cell was prepared in the same manner as in Example 16 except that the pre-doped sheet produced in Example 13 was placed on the surface of the positive electrode and only the pre-doped layer was transferred to the surface of the positive electrode using a roll press machine. A charge / discharge test was performed. The total film thickness of the positive electrode, the separator, and the pre-doped sheet at this time was 126 μm. As a result, the discharge capacity in the third cycle was 0.19 mAh at 1C and 0.17 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 95% at 1C and 85% at 10C. The results are shown in Table 4.

(Example 23)
In Example 16, the coin cell was prepared and coin cell was prepared in the same manner as in Example 16 except that the pre-doped sheet produced in Example 14 was placed on the surface of the positive electrode and only the pre-doped layer was transferred to the surface of the positive electrode using a roll press machine. A charge / discharge test was performed. The total film thickness of the positive electrode, the separator, and the pre-doped sheet at this time was 133 μm. As a result, the discharge capacity in the third cycle was 0.20 mAh at 1C and 0.15 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 100% at 1C and 75% at 10C. The results are shown in Table 4.

(Example 24)
In Example 16, the coin cell was prepared and coin cell was prepared in the same manner as in Example 16 except that the pre-doped sheet produced in Example 15 was placed on the surface of the positive electrode and only the pre-doped layer was transferred to the surface of the positive electrode using a roll press machine. A charge / discharge test was performed. The total film thickness of the positive electrode, the separator, and the pre-doped sheet at this time was 133 μm. As a result, the discharge capacity in the third cycle was 0.20 mAh at 1C and 0.13 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 100% at 1C and 65% at 10C. The results are shown in Table 4.

(Comparative Example 15)
In Example 16, a coin cell was prepared and a charge / discharge test was carried out in the same manner as in Example 16 except that the pre-doped sheet prepared in Comparative Example 4 was used. The total film thickness of the positive electrode and the separator at this time was 135 μm. As a result, the discharge capacity in the third cycle was 0.05 mAh at 1 C and 0.02 mAh at 10 C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 25% at 1C and 10% at 10C. The results are shown in Table 4.

(Comparative Example 16)
In Example 16, a coin cell was prepared and a charge / discharge test was carried out in the same manner as in Example 16 except that the pre-doped sheet prepared in Comparative Example 5 was used. The total film thickness of the positive electrode and the separator at this time was 128 μm. As a result, the discharge capacity in the third cycle was 0.04 mAh at 1C and 0.02 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 20% at 1C and 10% at 10C. The results are shown in Table 4.

(Comparative Example 17)
In Example 16, a coin cell was produced in the same manner as in Example 16 except that the pre-doped agent mixed positive electrode produced in Comparative Example 6 was used as the positive electrode and a cellulose-based non-woven fabric (TF40 manufactured by Nippon Kodoshi Kogyo Co., Ltd.) was used as the separator. And a charge / discharge test was performed. The total film thickness of the positive electrode and the separator at this time was 122 μm. As a result, the discharge capacity in the third cycle was 0.08 mAh at 1C and 0.04 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 40% at 1C and 20% at 10C. The results are shown in Table 4.

(Comparative Example 18)
In Example 16, a coin cell was produced in the same manner as in Example 16 except that the pre-doped agent mixed positive electrode produced in Comparative Example 7 was used as the positive electrode and a cellulose-based non-woven fabric (TF40 manufactured by Nippon Kodoshi Kogyo Co., Ltd.) was used as the separator. And a charge / discharge test was performed. The total film thickness of the positive electrode and the separator at this time was 124 μm. As a result, the discharge capacity in the third cycle was 0.09 mAh at 1C and 0.04 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 45% at 1C and 20% at 10C. The results are shown in Table 4.

(Comparative Example 19)
In Example 16, a coin cell was produced in the same manner as in Example 16 except that the pre-doped agent mixed positive electrode produced in Comparative Example 8 was used as the positive electrode and a cellulose-based non-woven fabric (TF40 manufactured by Nippon Kodoshi Kogyo Co., Ltd.) was used as the separator. And a charge / discharge test was performed. The total film thickness of the positive electrode and the separator at this time was 128 μm. As a result, the discharge capacity in the third cycle was 0.10 mAh at 1C and 0.05 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 50% at 1C and 25% at 10C. The results are shown in Table 4.

(Comparative Example 20)
In Example 16, a coin cell was produced in the same manner as in Example 16 except that the pre-doped agent mixed positive electrode produced in Comparative Example 9 was used as the positive electrode and a cellulose-based non-woven fabric (TF40 manufactured by Nippon Kodoshi Kogyo Co., Ltd.) was used as the separator. And a charge / discharge test was performed. The total film thickness of the positive electrode and the separator at this time was 137 μm. As a result, the discharge capacity in the third cycle was 0.18 mAh at 1C and 0.07 mAh at 10C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 90% at 1C and 35% at 10C. The results are shown in Table 4.

(Comparative Example 21)
In Example 16, a coin cell was prepared and a charge / discharge test was performed in the same manner as in Example 16 except that a cellulose-based non-woven fabric (TF40 manufactured by Nippon Kodoshi Kogyo Co., Ltd.) was used as a separator. The total film thickness of the positive electrode and the separator at this time was 114 μm. As a result, the discharge capacity in the third cycle was 0.05 mAh at 1 C and 0.02 mAh at 10 C. Since the design capacity was 0.2 mAh, the realization rate of the design capacity was 25% at 1C and 10% at 10C. The results are shown in Table 4.

1 Pre-doped sheet or electrode 2 Iron rod (diameter 1.0 cm)

Claims

A pre-doped sheet for a power storage device containing a pre-doping agent containing a lithium metal composite oxide.
The lithium metal composite oxide contains lithium (Li) and at least one metal element (Me) selected from the group consisting of Fe, Al, Mn and Co.
The lithium metal composite oxide has an inverted fluorite-type structure and has an inverted fluorite-type structure.
The Li / Me (molar ratio) of the lithium metal composite oxide satisfies 3.0 <Li / Me ≦ 7.5, and
A pre-doped sheet for a power storage device, wherein the content (X) of the pre-doping agent satisfies 0.3 <X <6.0 mg / cm 2.
In the X-ray diffraction measurement, the lithium metal composite oxide was 2θ (diffraction angle) = 23.7 ± 0.5 °, 33.6 ± 0.7 °, 36.5 ± 0.7 ° and 56.7. The pre-doped sheet according to claim 1, which has any diffraction peak intensity of ± 0.5 °.
Separator for power storage device including the pre-doped sheet according to claim 1 or 2.
A power storage device including the pre-doped sheet according to claim 1 or 2.
A method for producing a pre-doped sheet for a power storage device containing a pre-doping agent containing a lithium metal composite oxide.
The method for producing a pre-doped sheet according to claim 1 or 2, wherein a coating material containing the pre-doping agent and an organic solvent is applied to the surface of the porous sheet base material.
A method for producing a pre-doped sheet for a power storage device containing a pre-doping agent containing a lithium metal composite oxide.
The method for producing a pre-doped sheet according to claim 1 or 2, wherein the pre-doping agent is kneaded into a resin and molded.
A method for producing a pre-doped sheet for a power storage device containing a pre-doping agent containing a lithium metal composite oxide.
The method for producing a pre-doped sheet according to claim 1 or 2, wherein a coating material containing the pre-doping agent and an organic solvent is applied to the surface of the release film base material.