JP7027825B2 - Manufacturing method of lithium-ion power storage device and lithium-ion power storage device - Google Patents

Description

The present invention relates to a method for manufacturing a lithium ion power storage device and a lithium ion power storage device manufactured by the manufacturing method.

In power storage devices such as lithium ion batteries and capacitors, a technique for increasing the capacity and voltage of a power storage device by preliminarily carrying lithium ions on an active material (hereinafter referred to as predoped) is attracting attention. As a practical pre-doping method, for example, a method is known in which a lithium metal foil is attached to an electrode containing an active material to bring it into contact with the electrode, and after injection of an electrolytic solution, lithium is doped into the active material. This technology is effective for coin-type batteries that have a small number of electrodes and use relatively thick electrodes, but the battery manufacturing process is complicated for laminated structure batteries and wound structure batteries in which a plurality of thin electrodes are laminated. There is a problem of becoming.

Under such circumstances, a simple and practical pre-doping method in the manufacturing process of a lithium ion storage device having a large capacity, the progress of lithium ion doping, and whether or not the required amount of lithium ions have been doped can be easily confirmed. Development of a method is required.

Patent Document 1 discloses an organic electrolyte battery having a laminated unit of a positive electrode and a negative electrode provided with a current collector having a through hole, and subjected to lithium predoping. However, in order to confirm the progress of lithium ion doping to the electrode and whether the required amount of lithium ion was doped, the battery was once disassembled, and the reduction of the lithium ion supply source was confirmed or disassembled respectively. A complicated process of manufacturing a half-cell having an electrode and a lithium metal as a counter electrode and checking the capacity is required (Patent Document 1).

International Publication No. 00/07255

An object of the present invention is to provide a method for easily confirming the progress of lithium ion doping and whether or not a required amount of lithium ions has been doped in the process of manufacturing a lithium ion storage device.

As a result of diligent studies, the present inventors connect a conductor piece to one or more electrodes including an electrode located at the most distant position from a lithium ion source in a group of electrodes targeted for lithium ion doping. Then, the progress of doping is easily confirmed by exposing each conductor piece to the outside of the lithium ion storage device so as not to contact each other and measuring the open circuit voltage of each electrode to which the conductor piece is connected. We found that we could do it, and completed the present invention.

That is, the present invention
[1] A laminated body in which a positive electrode and a negative electrode are laminated, a lithium ion supply source arranged on at least one side of the laminated body in the stacking direction, and an electrolytic solution are sealed and supplied from the lithium ion supply source in a sealed state. A method for manufacturing a lithium ion storage device, which comprises a step of doping a positive electrode group or a negative electrode group with lithium ions.
In the group of electrodes targeted for lithium ion doping, a connection step of electrically connecting a piece of conductor to one or more electrodes including an electrode located at a position farthest from a lithium ion source, and a connection step.
A sealing process in which the conductor pieces are exposed to the outside of the lithium ion storage device so as not to come into contact with each other to seal the laminate, the lithium ion source, and the electrolytic solution.
A lithium ion storage device comprising: a determination step of measuring the open circuit voltage of each electrode to which the conductor piece is connected via each conductor piece and determining the completion of doping based on each measured voltage. Manufacturing method,
[2] Further including a step of connecting a conductor piece to a lithium ion supply source.
In the sealing step, the conductor pieces connected to the lithium ion supply source are exposed to the outside of the lithium ion storage device so as not to come into contact with the respective conductor pieces, and the laminate, the lithium ion supply source and the electrolytic solution are sealed. ,
The determination step is characterized in that the open circuit voltage of each electrode to which the conductor piece is connected is measured by using the conductor piece connected to the lithium ion supply source and using the lithium ion supply source as a reference electrode [1]. ] The manufacturing method described in
[3] A laminated body in which a positive electrode and a negative electrode are laminated, a lithium ion supply source arranged on at least one side of the laminated body in the stacking direction, and an electrolytic solution are sealed and supplied from the lithium ion supply source in a sealed state. A method for manufacturing a lithium ion storage device, which comprises a step of doping a positive electrode group or a negative electrode group with lithium ions.
In a group of electrodes targeted for lithium ion doping, lithium ions so that some of the current collectors in one or more electrodes, including the electrode located most distant from the lithium ion source, do not come into contact with each other. A sealing process that exposes the outside of the power storage device to seal the laminate, lithium ion source, and electrolyte.
A method for manufacturing a lithium ion power storage device, which comprises a determination step of measuring an open circuit voltage of each electrode on which a part of a current collector is exposed and determining completion of doping based on each measured voltage.
[4] In the sealing step, a part of the current collector in the lithium ion supply source is exposed to the outside of the lithium ion storage device so as not to come into contact with the part of the current collector in the one or a plurality of electrodes. , Sealing the laminate, lithium ion source and electrolyte,
In the determination step, a part of the current collector in the lithium ion supply source is used, and the open circuit voltage of each electrode to which a part of the current collector is exposed is measured using the lithium ion supply source as a reference electrode. The manufacturing method according to [3], which is characterized by
[5] The description according to any one of [1] to [4], wherein in the determination step, the voltage after a predetermined time has elapsed from the start of the measurement of the open circuit voltage is used as the measurement voltage. Manufacturing method,
[6] The manufacturing method according to any one of [1] to [5], wherein each positive electrode and each negative electrode have through holes penetrating in the stacking direction.
[7] Of [1] to [6], the through-holes formed in each positive electrode and each negative electrode have an opening diameter of 0.05 mm or more and an opening ratio of 1.0% or more. The manufacturing method described in any one,
[8] The positive electrode and the negative electrode are laminated so that the positions of the through holes formed in each positive electrode and the positions of the through holes formed in each negative electrode coincide with each other [1] to [. 7] The manufacturing method according to any one of
[9] The production method according to any one of [1] to [8], wherein the active material used for the positive electrode is a sulfur-based active material having a total sulfur content of 50% by mass or more by elemental analysis.
[10] The active material used for the positive electrode contains a carbon-sulfur structure having peaks near 500 cm ^-1 and 1250 cm ^-1 and around 1450 cm ^-1 of the Raman shift in the Raman spectrum [1] to [ 9] The manufacturing method according to any one of
[11] A lithium ion storage device including a laminate in which a positive electrode and a negative electrode are laminated, and a lithium ion supply source arranged on at least one side in the stacking direction of the laminate, which is the farthest from the lithium ion supply source. Lithium-ion storage is characterized in that conductor pieces are connected to one or more electrodes including electrodes arranged in the above-positioned positions, and each conductor piece is exposed to the outside of a lithium-ion storage device so as not to contact each other. device,
[12] A lithium ion storage device including a laminate in which a positive electrode and a negative electrode are laminated, and a lithium ion supply source arranged on at least one side in the stacking direction of the laminate.
It is characterized in that a part of the current collector in one or more electrodes including the electrode located at the farthest position from the lithium ion source is exposed to the outside of the lithium ion storage device so as not to contact each other. Lithium-ion storage device,
Regarding.

According to the present invention, it is possible to easily confirm the progress of lithium ion doping and whether or not the required amount of lithium ions has been doped in the manufacturing process of the lithium ion storage device. The lithium ion storage device according to the present embodiment is designed so that the tabs of the respective electrodes to be doped do not come into contact with each other, and since lithium metal is used as a lithium source and a reference electrode, the respective electrodes and the reference electrode are used. The potential difference between the two and the electrode can be measured, and the progress of doping at each electrode and whether or not the required amount of doping has been achieved can be confirmed without disassembling the power storage device, which is highly convenient.

It is sectional drawing which shows typically the reaction apparatus used for the production of a sulfur-based active material. It is a graph which shows the result of Raman spectrum analysis of the sulfur-based active material obtained in Example 1. FIG. It is a graph which shows the result of FT-IR spectrum analysis of the sulfur-based active material obtained in Example 1. FIG. It is a schematic diagram of the electrode arrangement in the lithium ion power storage device which concerns on this embodiment.

The configuration of the lithium ion power storage device and the manufacturing method thereof according to the present embodiment will be described below.

<Electrode configuration>
The positive electrode and the negative electrode according to the present embodiment can have the same structure as a general lithium ion power storage device. For example, the electrode for a lithium ion secondary battery according to the present embodiment can be produced by applying an electrode material in which an active material, a conductive auxiliary agent, a binder, and a solvent are mixed to a current collector.

(Current collector)
As the current collector, one generally used as an electrode for a lithium ion secondary battery can be used. Specific examples of the current collector include aluminum-based current collectors such as aluminum foil, aluminum mesh, punching aluminum sheet, and aluminum expand sheet; stainless steel foil, stainless steel mesh, punching stainless steel sheet, stainless steel expand sheet, and the like. Stainless steel collectors; Nickel-based collectors such as foamed nickel and nickel non-woven fabrics; Copper-based collectors such as copper foil, copper mesh, punching copper sheet, and copper expanded sheet; Titanium-based collectors such as titanium foil and titanium mesh. Current collector; Examples thereof include carbon-based current collectors such as carbon non-woven fabrics and carbon woven fabrics. Among them, an aluminum-based current collector is preferable from the viewpoints of mechanical strength, conductivity, mass density, cost and the like. Further, since the carbon non-woven fabric made of carbon having a high degree of graphitization and / or the current collector made of carbon woven fabric does not contain hydrogen and has low reactivity with sulfur, it can be used as a current collector for sulfur-based active materials. Suitable. Examples of the raw material of carbon fiber having a high degree of graphitization include various pitches (that is, by-products such as petroleum, coal, coal tar) and polyacrylonitrile fiber (PAN) which are materials of carbon fiber.

The shape of the current collector is not particularly limited, but for example, a foil-like base material, a three-dimensional base material, or the like can be used. By using a three-dimensional base material (foamed metal, mesh, woven fabric, non-woven fabric, expand, etc.), an electrode with high capacitance density can be obtained even with a binder that lacks adhesion to the current collector, and the rate is high. The charge / discharge characteristics also tend to be good.

(Positive electrode active material)
The positive electrode active material is not particularly limited as long as it is a compound that can occlude and release lithium ions. Specific examples of the positive electrode active material include, for example, a metal composite oxide of lithium and a transition metal such as a lithium manganese-based composite oxide, a lithium cobalt-based composite oxide, and a lithium nickel-based composite oxide, a sulfur-based active material, and the like. However, from the viewpoint of cost, safety and high capacity, a sulfur-based active material is preferably used.

In the present embodiment, the "sulfur-based active material" refers to an active material containing a sulfur element as a constituent element, for example, elemental sulfur (S), titanium sulfide, molybdenum sulfide, iron sulfide, copper sulfide, and the like. Examples thereof include compounds containing sulfur elements such as nickel sulfide, lithium sulfide, and organic disulfide compounds. Further, an active material (carbon-sulfur composite active material) in which sulfur and a carbon material or the like are combined is also preferably used.

As the carbon-sulfur composite active material, a carbon-sulfur structure having a thienoacene structure is particularly preferably used. A lithium ion secondary battery using the carbon sulfur structure as a positive electrode has a large charge / discharge capacity and excellent cycle characteristics.

で表されるようにチオフェン環が縮合して連鎖した長鎖ポリマー状のチエノアセン構造を有していると推測される。 The carbon-sulfur structure has peaks in the Raman spectrum near 500 cm ^-1 and 1250 cm ^-1 and around 1450 cm ^-1 of the Raman shift. This spectrum is different from the spectrum called the D band near 1350 cm ^-1 and the G band near 1590 cm ^-1 found in the 6-membered graphite structure, and the literature [Chem. Phys. Chem. 2009, 10 , 3069-3076], the carbon-sulfur structure showing the Raman spectrum described above is of formula (i).

As represented by, it is presumed that the thiophene ring has a long-chain polymer-like thienoasen structure fused and chained.

Further, the carbon-sulfur structure preferably has a hydrogen content of 1.6% by mass or less, particularly preferably 1.0% by mass or less. In addition, in the FT-IR spectrum, peaks may be present near 917 cm ^-1 , 1042 cm ^-1 , 1149 cm ^-1 , 1214 cm ^-1 , 1388 cm ^-1 , 1415 cm ^-1 , and 1439 cm ^-1 . preferable.

The carbon sulfur structure is heat-treated by blending sulfur, a vulcanization accelerator and / or a conductive powder with unvulcanized diene-based rubber, for example, according to the method described in JP-A-2015-92449. Can be manufactured. The produced carbon-sulfur structure can be pulverized to have a predetermined particle size and classified into particles suitable for producing a positive electrode.

The higher the total sulfur content in the sulfur-based active material, the better the cycle characteristics of the lithium-ion secondary battery tend to be. Therefore, the total content of sulfur in the sulfur-based active material by elemental analysis is preferably 50% by mass or more.

When the sulfur-based active material is a carbon-sulfur composite active material, the amount of sulfur incorporated into the molecule of the carbon-sulfur structure is small, or a network of sufficient size that can enclose elemental sulfur cannot be formed. Or, as a result of the electron conductivity of the carbon-sulfur structure being lowered, the charge / discharge capacity of the lithium ion secondary battery may be reduced. In addition, the elution of sulfur into the electrolytic solution cannot be sufficiently suppressed, and the cycle characteristics may deteriorate.

In a system in which a carbon material having a graphite structure is blended as the conductive powder, the sulfur content may fall below the above range due to the influence of the carbon constituting the carbon material, but the lithium ion battery is still present. It can have the effect of improving the cycle characteristics of the next battery. However, the sulfur content in that case is preferably 45% by mass or more in order to maintain the effect of improving the cycle characteristics of the lithium ion secondary battery.

(Conductive aid)
Examples of the conductive auxiliary agent include vapor grown carbon fiber (VGCF), carbon powder, carbon black (CB), acetylene black (AB), Ketjen black (KB), graphite, graphene, and carbon tube. Such as carbon-based conductive auxiliary agents; fine powders of metals stable at a positive electrode potential such as aluminum and titanium may be used, and one of these may be used, or two or more thereof may be used in combination. From the viewpoint of capacitance density and input / output characteristics, a carbon-based conductive auxiliary agent is preferable, and from the viewpoint of conductivity and cost, acetylene black (AB) or Ketjen black (KB) is more preferable.

(Binder)
Examples of the binder include polyvinylidene fluoride (PVdF), polyethylene tetrafluoride (PTFE), styrene-butadiene rubber (SBR), polyimide (PI), polyamideimide (PAI), polyvinyl chloride (PVC), and polyacrylonitrile. (PAN), modified polyvinylidene oxide (PPO), polyethylene oxide (PEO), polyethylene (PE), polypropylene (PP), hydroxypropyl cellulose (HPC), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), acrylic resin, etc. Can be mentioned. From the viewpoint of reducing the load on the environment and the human body, an aqueous binder such as hydroxypropyl cellulose (HPC), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), or acrylic resin is preferable. These binders may be used alone or in combination of two or more.

(solvent)
Examples of the solvent include one or more selected from N-methyl-2-pyrrolidone, N, N-dimethylformaldehyde, alcohol, water and the like. Water is preferable from the viewpoint of reducing the load on the environment and the human body.

(Negative electrode material)
Examples of the negative electrode material constituting the negative electrode of the lithium ion secondary battery include carbon-based materials such as metallic lithium and graphite, silicon thin films, silicon-based materials such as SiO, and tin alloy-based materials such as copper-tin and cobalt-tin. Examples thereof include known negative electrode materials such as. When a lithium-free material such as a carbon-based material, a silicon-based material, or an alloy-based material is used as the negative electrode material, a short circuit between the positive and negative electrodes due to the generation of dendrite can be less likely to occur, and the lithium ion secondary battery can be used. The life can be extended. Of these, silicon-based materials, which are high-capacity negative electrode materials, are preferable, and thin-film silicon, which can reduce the electrode thickness and is advantageous in terms of capacity per volume, is more preferable.

The electrode according to the present embodiment is, for example, mixed with an active material, a conductive additive, a binder, and a solvent and sufficiently kneaded to prepare a uniform slurry, and then the slurry is applied to a current collector and dried. It is formed by. The blending ratio of each of the above components is not particularly limited, but for example, 3 to 50 parts by mass of the conductive additive, 3 to 50 parts by mass of the binder, and an appropriate amount of solvent can be blended with 100 parts by mass of the active material.

The electrode according to the present embodiment is characterized in that a current collector coated with an active material is perforated to form a through hole penetrating in the thickness direction of the electrode. By applying the active material to the current collector and then drilling the current collector and the active material layer together, it becomes very easy to process and manufacture the electrodes, and when pre-doping lithium ions, pre-doping is performed. Progresses efficiently.

When opening a hole, a general method such as machining such as punching or laser processing can be used. The arrangement of the openings is not particularly limited, and may be a general type such as a staggered type, a square staggered type, or a parallel type. The shape of the opening is not particularly limited, but a circle is common.

The opening diameter of the electrode is preferably 0.05 mm or more, more preferably 0.1 mm or more, still more preferably 0.2 mm or more, from the viewpoint of doping progress efficiency. Further, from the viewpoint of the energy density of the battery, 5.0 mm or less is preferable, 3.0 mm or less is more preferable, and 2.0 mm or less is further preferable.

The aperture ratio of the electrode is preferably 1.0% or more, more preferably 3.0% or more, still more preferably 5.0% or more, from the viewpoint of the progress efficiency of doping. Further, from the viewpoint of the energy density of the battery, 50% or less is preferable, 45% or less is more preferable, and 40% or less is further preferable.

From the viewpoint of the energy density of the battery, the electrode basis weight is preferably 0.1 mAh / cm ² , more preferably 0.5 mAh / cm ² or more, and even more preferably 1.0 mAh / cm ² or more.

The distance between the openings is preferably 1 mm to 20 mm, more preferably 1.5 m to 15 mm, still more preferably 2 mm to 10 mm.

The thickness of the electrode including the current collector is preferably 10 μm to 500 μm, more preferably 30 μm to 400 μm, and further preferably 50 μm to 300 μm.

<Lithium ion feeder>
As the lithium ion feeder, a single lithium metal (Li), a lithium alloy compound such as a lithium-aluminum alloy, a lithium compound, or the like can be used. Specific examples of the lithium compound include LiFeO ₂ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , Li ₅ FeO ₄ , Li ₂ MnO ₃ , LiFePO ₄ , LiV ₂ O ₄ , and the like.

A conductive porous body such as a stainless steel mesh is used as the lithium metal current collector, and the pores of the conductive porous body are preferably filled with 80% or more of the lithium metal and arranged, whereby lithium is doped. Also, the gaps created between the electrodes due to the disappearance of lithium can be reduced, and lithium can be smoothly supported on the active material.

<Electrolyte>
The electrolyte constituting the lithium ion secondary battery may be any liquid or solid having ionic conductivity, and the same electrolyte as that used for known lithium ion secondary batteries can be used, but the output characteristics of the battery are From the viewpoint of high cost, it is preferable to use an organic solvent in which an alkali metal salt as a supporting electrolyte is dissolved.

Examples of the organic solvent include at least one selected from non-aqueous solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl ether, γ-butyrolactone and acetonitrile. Preferred are ethylene carbonate, propylene carbonate, or a mixed solvent thereof.

Examples of the supporting electrolyte include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiI, LiClO ₄ , and the like, and LiPF ₆ is preferable.

The concentration of the supporting electrolyte may be about 0.5 mol / L to 1.7 mol / L. The electrolyte is not limited to liquid. For example, when the lithium ion secondary battery is a lithium polymer secondary battery, the electrolyte may be a solid state (for example, a polymer gel state), an ionic liquid, a molten salt, or the like.

<Separator>
The separator intervenes between the positive electrode and the negative electrode to allow the movement of ions between the two electrodes, and functions to prevent an internal short circuit between the positive electrode and the negative electrode. If the lithium-ion secondary battery is a closed type, the separator is also required to have a function of holding an electrolytic solution.

As the separator, for example, a thin-walled, microporous or non-woven fabric made of polyethylene, polypropylene, polyacrylonitrile, aramid, polyimide, cellulose, glass or the like is preferably used.

The pore size of the separator is preferably 1 μm to 1000 μm, more preferably 10 μm to 500 μm, and even more preferably 10 μm to 200 μm.

The thickness of the separator is preferably 1 μm to 100 μm, more preferably 5 μm to 50 μm, and even more preferably 10 μm to 40 μm.

The porosity of the separator is preferably 10% to 90%, more preferably 30% to 85%, and even more preferably 50% to 80%.

The fiber diameter of the separator is preferably 0.001 μm to 100 μm, more preferably 0.01 μm to 20 μm, and even more preferably 0.1 μm to 10 μm.

FIG. 4 shows a schematic diagram of the electrode arrangement in the lithium ion power storage device according to the present embodiment. Each positive electrode 13 and each negative electrode 14 formed by applying an active material to both sides of the current collector and drilling the current collectors are alternately arranged via a separator to form a laminated body. Further, the lithium ion feeder 15 is arranged via a separator on at least one side of the laminated body in the stacking direction, preferably on the outermost layers on both sides to form a laminated laminated cell. It is preferable that the positive electrode 13 and the negative electrode 14 are laminated so that the positions of the through holes 17 formed in each positive electrode 13 and the positions of the through holes 17 formed in each negative electrode 14 coincide with each other. In the present embodiment, the laminated body is not limited to the one in which a plurality of positive electrodes 13 and 14 are alternately laminated, but also the one in which one layer of each of the positive electrode 13 and the negative electrode 14 is laminated, or one of the positive electrode 13 and the negative electrode 14. May be sandwiched between the other electrodes.

<Confirmation of pre-dope>
In the doping step, the electrode at the end of the battery structure and the lithium ion feeder 15 may be short-circuited, and the active material may be doped with lithium ions. Alternatively, a voltage may be applied between the positive electrode 13 or the negative electrode 14 and the lithium ion feeder 15 to dope the lithium ions. The target electrode for doping may be either the positive electrode 13 or the negative electrode 14.

In order to measure the potential at the time of pre-doping, for example, the conductor piece (tab) 16 can be connected to one or more electrodes including the electrode arranged at the position farthest from the lithium ion feeder 15. Further, if necessary, the conductor piece (tab) 16 may be connected to the lithium ion feeder 15. Alternatively, instead of using a conductor piece, a collector in one or more electrodes, including an electrode located most distant from the lithium ion source, is partially lithium when the lithium ion storage device is configured. It may be processed in advance into a shape that is exposed to the outside of the ion storage device. Similarly, the current collector in the lithium ion feeder may be pre-processed into a shape such that a part of the current collector is exposed to the outside of the lithium ion power storage device when the lithium ion power storage device is configured.

The progress of doping can be confirmed by measuring the open circuit voltage (Open Circuit Voltage: OCV) of each of the doped electrodes. When the doping is completed, the difference between the reference electrode (lithium metal) and the reference electrode (lithium metal) at each electrode is small, and the difference in OCV depending on the stacking position (distance from the lithium ion feeder 15) is also small. For example, when the difference in OCV between the negative electrode 14 closest to the lithium ion feeder 15 and the negative electrode 14 farthest from the lithium ion feeder 15 is 0.01 V or less, it can be used as a guide for determining that lithium doping is completed.

In this case, it is preferable to measure the OCV after a certain period of time has elapsed from the start of the OCV measurement. When the predoping is not completed, the potential close to that of the reference electrode is shown immediately after the start of OCV measurement, but the potential gradually increases after a lapse of time. In the lithium ion storage device according to the present embodiment, the actual capacity of the battery is the design capacity when the OCV at least 500 seconds after the start of OCV measurement is the same as the OCV immediately after doping, that is, the OCV at the start of OCV measurement. It has been confirmed that the value is equivalent to that of. From this, for example, when the difference between the OCV immediately after doping and the OCV after 500 seconds is 0.01V or less, it can be used as a guide for determining that the pre-doping is completed.

The shape of the lithium ion secondary battery according to the present embodiment is not particularly limited, and various shapes such as a cylindrical type, a laminated type, a coin type, and a button type can be used.

Hereinafter, embodiments for carrying out the present invention will be described. The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

<< Example 1 >>
<Manufacturing of sulfur-based active substances>
(Preparation of raw material compound)
As the diene rubber, high cis butadiene rubber [UBEPOL (registered trademark) BR150L manufactured by Ube Kosan Co., Ltd., cis 1,4 bond content 98% by mass] is used, and as the conductive carbon material, manufactured by Denka Co., Ltd. Denka Black is used, precipitated sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. is used as sulfur, and zinc diethyldithiocarbamate manufactured by Ouchi Shinko Chemical Industry Co., Ltd. as a vulcanization accelerator (registered trademark). EZ] was used.

1000 parts by mass of precipitated sulfur, 20 parts by mass of conductive carbon material, and 25 parts by mass of vulcanization accelerator are mixed with 100 parts by mass of the above high-cis butadiene rubber, and a kneading test device [Mix Lab manufactured by Moriyama Co., Ltd.] is used. The raw material compound was obtained by kneading using. The obtained raw material compound was finely crushed with a cutter mill and subjected to a heat treatment step.

(Reactor)
The reactor 1 shown in FIG. 1 was used for the heat treatment of the raw material compound 2. The reaction apparatus 1 is a reaction vessel 3 having an outer diameter of 60 mm, an inner diameter of 50 mm, and a height of 300 mm, which is made of quartz glass having a bottomed tubular shape for accommodating the raw material compound 2 and heat-treating, and the upper opening of the reaction vessel 3. Closed Silicone lid 4, one alumina protective tube 5 penetrating the lid 4 ("Alumina SSA-S" manufactured by Nikkato Co., Ltd., outer diameter 4 mm, inner diameter 2 mm, length 250 mm), glass introduction tube 6 and gas discharge pipe 7 (both are "alumina SSA-S" manufactured by Nikkato Co., Ltd., outer diameter 6 mm, inner diameter 4 mm, length 150 mm), and an electric furnace 8 (rutsubo) that heats the reaction vessel 3 from the bottom side. It is equipped with a furnace, an opening width of φ80 mm, and a heating height of 100 mm).

The alumina tube 5 is formed so as to have a length below the lid 4 so as to reach the raw material compound 2 housed in the bottom of the reaction vessel 3, and a thermocouple 9 is inserted therein. The alumina protective tube 5 is used as a protective tube for the thermocouple 9. The tip of the thermocouple 9 is inserted into the raw material compound 2 while being protected by the closed tip of the alumina protective tube 5, and functions to measure the temperature of the raw material compound 2. The output of the thermocouple 9 is input to the temperature controller 10 of the electric furnace 8 as shown by the solid arrow in the figure, and the temperature controller 10 receives the heating temperature of the electric furnace 8 based on the input from the thermocouple 9. Functions to control.

The gas introduction pipe 6 and the gas discharge pipe 7 are formed so that the lower ends thereof project downward by 3 mm from the lid 4. Further, the upper portion of the reaction vessel 3 protrudes from the electric furnace 8 and is exposed to the outside air. Therefore, the vapor of sulfur generated from the raw material compound by heating the reaction vessel 3 rises upward of the reaction vessel 3 as shown by the arrow of the alternate long and short dash line in the figure, but is cooled in the middle and becomes droplets. As shown by the broken line arrow in the figure, it is dropped and refluxed. Therefore, sulfur in the reaction system does not leak to the outside through the glass discharge pipe 7.

Argon gas is continuously supplied to the gas introduction pipe 6 from a gas supply system (not shown). Further, the gas discharge pipe 7 is connected to a trap tank 12 containing the sodium hydroxide aqueous solution 11. The exhaust gas that is going to go out from the reaction vessel 3 through the gas discharge pipe 7 is once passed through the sodium hydroxide aqueous solution 11 in the trap tank 12 and then discharged to the outside. Therefore, even if hydrogen sulfide gas generated by the vulcanization reaction is contained in the exhaust, it is neutralized with the sodium hydroxide aqueous solution and removed from the exhaust.

(Heat treatment process)
While the raw material compound 2 was housed in the bottom of the reaction vessel 3, argon gas was continuously supplied from the gas supply system at a flow rate of 80 mL / min, and heating by the electric furnace 8 was started 30 minutes after the start of supply. The heating rate was 150 ° C./hour. Then, when the temperature of the raw material compound reached 450 ° C., heat treatment was performed for 2 hours while maintaining 450 ° C. Then, while adjusting the flow rate of Ar gas, the temperature of the reaction product was naturally cooled to 25 ° C. under an atmosphere of argon gas, and then the reaction product was taken out from the reaction vessel 3.

(Removal of unreacted sulfur)
The reaction product was crushed in a mortar, 2 g of the crushed product was placed in a glass tube oven and heated at 250 ° C. for 3 hours with vacuum suction to remove unreacted sulfur (or only a trace amount of unreacted sulfur). (Not included) Sulfur-based active material was obtained. The rate of temperature rise was 10 ° C./min.

(Raman spectrum analysis)
The obtained sulfur-based active material was subjected to Raman spectrum analysis using a laser Raman microscope RAMAN-11 manufactured by Nanophoton Co., Ltd. under the conditions of excitation wavelength λ = 532 nm, graching: 600 gr / mm, and resolution: 2 cm ^-1 . (Fig. 2). In FIG. 2, the vertical axis shows the relative intensity and the horizontal axis shows the Raman shift (cm ^-1 ). The obtained sulfur-based active material has peaks near 500 cm ^-1 of Raman shift, around 1250 cm ^-1 , around 1450 cm ^-1 , and around 1940 cm ^-1 , and the result is that a large amount of sulfur mentioned above is present. It was confirmed that it was in good agreement with the elemental analysis result that hydrogen was taken in and decreased.

In addition, the spectrum in FIG. 2 is different from the spectra called the D band near 1350 cm ^{-1 and the G band near 1590 cm -1 found} in the graphite structure having a 6-membered ring. , 10, 3069-3076]. ..

(FT-IR spectrum analysis)
Using the Fourier transform infrared spectrophotometer IRAffinity ^- 1 manufactured by Shimadzu Corporation, the obtained sulfur-based active material has a resolution of 4 cm ^-1 , the number of integrations: 100 times, and a measurement range of 400 cm ^-1 to 4000 cm. Under the condition of ¹ , FT-IR spectrum analysis was performed by the diffuse reflection method (Fig. 3). In the FT-IR spectrum, the obtained sulfur-based active material was around 917 cm ^-1 , around 1042 cm ^-1 , around 1149 cm ^-1 , around 1214 cm ^-1 , around 1388 cm ^-1 , around 1415 cm ^-1 , and around 1439 cm ^-1 . There is a peak in, and it was confirmed that this result is in good agreement with the elemental analysis result that a large amount of sulfur is taken in and hydrogen is reduced.

<Manufacturing of lithium-ion secondary battery>
(Positive electrode)
Sulfur-based active material, conductive auxiliary agent (acetylene black (denka black manufactured by Denki Kagaku Kogyo Co., Ltd.) / VGCF = 4: 1 mixture), and aqueous acrylic resin in a ratio of 90: 5: 5 (mass ratio). Weighed, placed in a container, and stirred and mixed using a rotating and revolving mixer (ARE-250 manufactured by Shinky Co., Ltd.) while adjusting the viscosity using water as a dispersant to prepare a uniform slurry. The prepared slurry was coated on carbon-coated aluminum having a thickness of 15 μm using an applicator and dried at 150 ° C. for 3 hours to prepare a positive electrode 13 for a lithium ion secondary battery.

(Negative electrode)
Weigh graphite, acetylene black (Denka black manufactured by Denki Kagaku Kogyo Co., Ltd.), and PVdF at a ratio of 90: 5: 5 (mass ratio), put them in a container, and adjust the viscosity using water as a dispersant. While doing so, stirring and mixing were carried out using a rotation / revolution mixer (ARE-250 manufactured by Shinky Co., Ltd.) to prepare a uniform slurry. The prepared slurry was applied onto a copper foil having a thickness of 10 μm using an applicator, and heated at 150 ° C. for 3 hours in a dryer to prepare a negative electrode 14.

(Processing of electrodes)
The positive electrode 13 and the negative electrode 14 were drilled with a laser processing machine with a predetermined opening diameter and aperture ratio. The shape of the perforations (through holes 17) was circular, and the arrangement was square staggered (45 ° staggered). Further, the positive electrode 13 and the negative electrode 14 that had been perforated were cut out so that the coated portion had a size of 50 mm × 50 mm. Further, each negative electrode 14 was tabbed so that the open circuit voltage (OCV) could be measured independently.

(Lithium ion feeder)
The lithium ion feeder 15 was configured by attaching a lithium metal foil to a current collector made of a conductive porous body such as a stainless mesh. In addition, tabbing was performed in the same manner as the negative electrode.

(Electrolytic solution)
As the electrolytic solution, a non-aqueous electrolyte in which LiPF ₆ was dissolved in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a ratio of 1: 1 and the concentration was 1.0 mol / L was used.

(Battery production)
In the dry room, each of the positive electrode 13 (11 sheets) and each negative electrode 14 (12 sheets) formed by the above-mentioned drilling process is passed through a separator (Celgard 2400 manufactured by Celgard, polypropylene microporous film having a thickness of 25 μm). They were arranged alternately to form a laminated body. Further, a lithium ion feeder 15 in which metallic lithium is attached to a stainless porous foil via a separator is arranged on the outermost layers on both sides, and a triode laminated unit composed of a positive electrode 13, a negative electrode 14, a lithium ion feeder 15, and a separator. Was produced. This triode laminated unit was packaged with an aluminum laminate which is an exterior body, and the above electrolytic solution was injected to prepare a power storage device. At this time, among the negative electrodes 14 to be doped with lithium ions, each conductor piece electrically connected to a plurality of negative electrodes 14 including the negative electrodes 14 arranged at the positions farthest from the lithium ion feeder 15 (at this time). The conductor pieces (not shown) electrically connected to the tab) 16 and the lithium ion feeder 15 were exposed to the outside of the lithium ion storage device so as not to come into contact with each other.

(Pre-dope)
After assembling the power storage device, the negative electrode 14 and the lithium ion feeder 15 were short-circuited to dope the negative electrode 14 with lithium ions for 10 days. After that, when the OCV of each negative electrode 14 was measured 500 seconds after the start of OCV measurement using the lithium ion feeder 15 as a reference electrode, the negative electrode potential of each negative electrode 14 was about 0.001 V, and any negative electrode 14 was used. It was confirmed that the lithium pre-doped was evenly formed.

According to the present invention, it is possible to easily confirm the progress of lithium ion doping and whether or not the required amount of lithium ions has been doped in the manufacturing process of the lithium ion storage device.

1 Reaction device 2 Raw material compound 3 Reaction vessel 4 Silicone lid 5 Alumina protective tube 6 Gas introduction tube 7 Gas discharge tube 8 Electric furnace 9 Thermoelectric pair 10 Temperature controller 11 Sodium hydroxide aqueous solution 12 Trap tank 13 Positive electrode 14 Negative electrode 15 Lithium ion Feeder 16 Conductor piece (tab)
17 through hole

Claims (12)

A laminated body in which a positive electrode and a negative electrode are laminated, a lithium ion supply source arranged on at least one side of the laminated body in the stacking direction, and an electrolytic solution are sealed, and lithium supplied from the lithium ion supply source in a sealed state. A method for manufacturing a lithium ion storage device, which comprises a step of doping a positive electrode group or a negative electrode group with ions.
In the group of electrodes targeted for lithium ion doping, a connection step of electrically connecting a piece of conductor to one or more electrodes including an electrode located at a position farthest from a lithium ion source, and a connection step.
A sealing process in which the conductor pieces are exposed to the outside of the lithium ion storage device so as not to come into contact with each other to seal the laminate, the lithium ion source, and the electrolytic solution.
The open circuit voltage of each electrode to which the conductor piece is connected is measured through each conductor piece, and the open circuit voltage at the start of measurement of the open circuit voltage and the open circuit voltage at least 500 seconds after the start of measurement of the open circuit voltage are opened. A method for manufacturing a lithium ion power storage device, which comprises a determination step of determining completion of doping when the difference from the circuit voltage is 0.01 V or less . Further including the step of connecting the conductor piece to the lithium ion source,
In the sealing step, the conductor pieces connected to the lithium ion supply source are exposed to the outside of the lithium ion storage device so as not to come into contact with the respective conductor pieces, and the laminate, the lithium ion supply source and the electrolytic solution are sealed. ,
The determination step is characterized in that the open circuit voltage of each electrode to which the conductor piece is connected is measured by using the conductor piece connected to the lithium ion supply source and using the lithium ion supply source as a reference electrode. The manufacturing method according to 1. A laminated body in which a positive electrode and a negative electrode are laminated, a lithium ion supply source arranged on at least one side of the laminated body in the stacking direction, and an electrolytic solution are sealed, and lithium supplied from the lithium ion supply source in a sealed state. A method for manufacturing a lithium ion storage device, which comprises a step of doping a positive electrode group or a negative electrode group with ions.
In a group of electrodes targeted for lithium ion doping, lithium ions so that some of the current collectors in one or more electrodes, including the electrode located most distant from the lithium ion source, do not come into contact with each other. A sealing process that exposes the outside of the power storage device to seal the laminate, lithium ion source, and electrolyte.
The open circuit voltage of each electrode with a part of the current collector exposed is measured, and the open circuit voltage at the start of measurement of the open circuit voltage and the open circuit voltage at least 500 seconds after the start of measurement of the open circuit voltage are A method for manufacturing a lithium ion storage device, which comprises a determination step of determining completion of doping when the difference is 0.01 V or less . In the sealing step, a part of the current collector in the lithium ion supply source is exposed to the outside of the lithium ion storage device so as not to come into contact with the part of the current collector in the one or a plurality of electrodes, and the laminated body is formed. , Seal the lithium ion source and electrolyte,
In the determination step, a part of the current collector in the lithium ion supply source is used, and the open circuit voltage of each electrode to which a part of the current collector is exposed is measured using the lithium ion supply source as a reference electrode. 3. The manufacturing method according to claim 3. The manufacturing method according to any one of claims 1 to 4 , wherein the positive electrode and the negative electrode each have through holes penetrating in the stacking direction. The invention according to any one of claims 1 to 5 , wherein the through-holes formed in each positive electrode and each negative electrode have an opening diameter of 0.05 mm or more and an opening ratio of 1.0% or more. The manufacturing method described. One of claims 1 to 6 , wherein the positive electrode and the negative electrode are laminated so that the positions of the through holes formed in each positive electrode and the positions of the through holes formed in each negative electrode coincide with each other. The manufacturing method according to paragraph 1. The production method according to any one of claims 1 to 7 , wherein the active material used for the positive electrode is a sulfur-based active material having a total sulfur content of 50% by mass or more by elemental analysis. Any of claims 1-8 , wherein the active material used for the positive electrode comprises a carbon sulfur structure having peaks in the Raman spectrum near 500 cm ^-1 and 1250 cm ^-1 and around 1450 cm ^-1 of the Raman shift. The manufacturing method according to paragraph 1. A lithium ion storage device including a laminated body in which a positive electrode and a negative electrode are laminated, and a lithium ion supply source arranged on at least one side of the laminated body in the stacking direction.
Through holes penetrating in the stacking direction are formed in each positive electrode and each negative electrode.
The positive electrode and the negative electrode are laminated so that the positions of the through holes formed in each positive electrode and the positions of the through holes formed in each negative electrode match.
A piece of conductor is connected to one or more electrodes, including the electrode located most distant from the lithium ion source.
A lithium ion power storage device characterized in that each conductor piece is exposed to the outside of the lithium ion power storage device so as not to come into contact with each other. A lithium ion storage device including a laminated body in which a positive electrode and a negative electrode are laminated, and a lithium ion supply source arranged on at least one side of the laminated body in the stacking direction.
Through holes penetrating in the stacking direction are formed in each positive electrode and each negative electrode.
The positive electrode and the negative electrode are laminated so that the positions of the through holes formed in each positive electrode and the positions of the through holes formed in each negative electrode match.
It is characterized in that a part of the current collector in one or more electrodes including the electrode located at the farthest position from the lithium ion source is exposed to the outside of the lithium ion storage device so as not to contact each other. Lithium-ion storage device. The basis weight of the positive and negative electrodes is 0.5 mAh / cm. ² The lithium ion power storage device according to claim 10 or 11, which is the above.

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