JP2011065983A - Scale-like thin film fine powder dispersion liquid or scale-like thin film fine powder, and paste using the same, electrode for battery, and lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scale-like thin-film fine powder dispersion liquid which can be used as a negative electrode of a lithium secondary battery superior in cycle characteristics while maintaining a storage and desorption performance of lithium which silicon originally has. <P>SOLUTION: The scale-like thin-film fine powder dispersion liquid contains in a solvent a scale-like thin-film fine powder capable of storage and adsorption of lithium in which any of thin-films is pulverized out of (A) a thin film by a layer of a single body or a laminate of a plurality of any of metal unit, alloy, or a metal compound capable of storage and desorption of lithium reversibly or (B) a thin film which is laminated to become a total two layers or more using both of a layer of a single body of any of metal unit, alloy, or a metal compound capable of storage and desorption of lithium reversibly and a layer of a single body of any of metal unit or alloy which is not capable of storage and desorption of lithium reversibly. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a scaly thin film fine powder dispersion or a scaly thin film fine powder. Specifically, the present invention is used for a negative electrode of a lithium secondary battery and maintains the high capacity of the lithium secondary battery while maintaining the battery life. The present invention relates to a scaly thin film fine powder dispersion that makes it possible to prolong the period of time.

  Since the lithium secondary battery was developed and announced for commercial use, it quickly became the mainstream of secondary batteries. This is because the standard voltage of the lithium secondary battery is 3.7 V, that is, it has an advantage that it is about 3 times that of the nickel cadmium battery and about 2 times that of the lead acid battery. Furthermore, it has a high energy density compared to other secondary batteries, low internal resistance, little decrease in battery capacity due to charging / discharging, that is, charging / discharging cycle characteristics are higher than other systems, that is, battery life is long, The fact that it has the advantage of being widely distributed is also a factor.

An example of the basic configuration of the lithium secondary battery is as follows.
A lithium transition metal oxide such as lithium cobaltate is used as the positive electrode (positive electrode plate), graphite (carbon) is used as the negative electrode (negative electrode plate), and several layers of each electrode plate are stacked to form an electrolyte. It consists of a structure formed by immersing in an ethylene carbonate (EC) -based electrolytic solution in which lithium fluorophosphate (LiPF ₆ ) is dissolved. In principle, each material of the positive electrode, the negative electrode, and the electrolyte only needs to be able to be charged / discharged by the transfer of electric charge due to the movement of lithium. Therefore, the present invention is not limited to the above and can have various configurations.

  Since the lithium secondary battery using carbon as a negative electrode has been commercialized, the energy density of the lithium secondary battery has improved more than twice. Currently, so-called mobile phones and laptop computers using lithium secondary batteries are used. While mobile devices are becoming more sophisticated, there is a problem that improving the energy density of conventional lithium secondary batteries using carbon as a negative electrode has almost reached its limit. That is, when carbon is used as the negative electrode, the cycle characteristics are good, but there is a problem that it cannot be increased until the initial charge capacity is required.

  Therefore, instead of using carbon for the negative electrode, a copper plate is used as a current collector, and thin copper amorphous silicon or microcrystalline silicon is laminated on the surface of this copper plate by chemical vapor deposition (CVD). Technology has been developed and used. This is because when silicon is used, the initial charge capacity can be increased as compared with the case where graphite is used. More specifically, the theoretical capacity of silicon is 4200 mAh / g, which is more than 10 times the theoretical capacity of graphite (372 mAh / g), which is why it is expected as a high-capacity negative electrode that can replace graphite.

  However, when silicon is used for the negative electrode, as the silicon negative electrode repeatedly expands and contracts as lithium is absorbed and desorbed, the cycle characteristics can be reduced by making the particles finer by cracking of the silicon particles or peeling from the copper plate used as the current collector. There was a problem of being bad.

  In other words, if such a phenomenon is repeated, the negative electrode may eventually be deformed, resulting in a decrease in the energy density of the battery, and the silicon that is laminated on the copper plate by repeating expansion and contraction. It is conceivable that the thin film will eventually be detached from the copper plate, resulting in deterioration of the cycle characteristics of the battery. That is, when silicon is used for the negative electrode, the cycle characteristics cannot be said to be preferable, and it cannot be said that it is better than that of graphite.

  Thus, for example, in the invention described in Patent Document 1, the amount of occlusion of lithium is suppressed by using a thin film in which copper is dissolved in silicon as the negative electrode material layer, and as a result, the expansion of the negative electrode material when lithium is occluded / desorbed. In other words, a material that suppresses deterioration of the negative electrode material due to expansion and contraction of the silicon negative electrode having a thin silicon film and has good cycle characteristics is disclosed.

JP 2002-289177 A

  However, in the invention described in Patent Document 1, a thin film in which silicon is dissolved in copper is laminated on the surface of the current collector. Although the effect may be avoided, it is based on the premise that silicon does not actively occlude lithium and presents a problem that the energy density cannot be maintained high. In addition, it is necessary to work to dissolve silicon in copper before laminating a thin film on the surface of the current collector, and an extra step is imposed in actual negative electrode production, which is not preferable. Moreover, even if silicon is dissolved in copper, it is not certain whether or not they are ideally evenly distributed and present, that is, the effect that was initially expected to be unevenly distributed between silicon and copper in the thin film. There was also a problem that it could not be obtained.

  On the other hand, when considering from the viewpoint of energy density, when a silicon negative electrode obtained by thinning silicon is used as a negative electrode of a practical lithium secondary battery, a film thickness of about 5 μm is required for the silicon thin film. However, when the film thickness is increased, the cycle characteristics of the silicon negative electrode are drastically deteriorated. As a result, it is very difficult to put a lithium secondary battery using a silicon thin film into practical use. In the invention described in Patent Document 1, although it is disclosed that the amount of occlusion of lithium is suppressed by using a thin film in which copper is solid-dissolved in silicon and the expansion of the negative electrode material is suppressed, In other words, the high energy density of silicon could not be used effectively, which was still a problem.

  Therefore, the present invention has been made in view of such problems, and the object thereof is to maintain cycle performance of a substance having a property capable of reversibly occluding and desorbing lithium while being excellent in cycle characteristics. Another object of the present invention is to provide a scaly thin film fine powder dispersion that can be used as a negative electrode of a lithium secondary battery.

  In order to solve the above-described problems, the invention relating to the scaly thin film fine powder dispersion according to claim 1 of the present invention provides (A) a simple metal, alloy, or metal capable of reversibly occluding and desorbing lithium. A thin film by a layer of any one of compounds, or a stack of a plurality of them, or (B) a layer of any one of a metal, alloy, or metal compound capable of reversibly inserting and extracting lithium, and lithium A thin film formed by laminating a total of two or more layers using both a single metal layer or an alloy layer that does not allow reversible storage and desorption. It is characterized in that a flaky fine powder capable of occluding and releasing lithium is finely pulverized and contained in a solvent.

  The invention according to claim 2 of the present invention comprises a release layer made of a resin on the surface of a polymer resin film that is a base film, and (A) a simple metal, alloy capable of reversibly occluding and desorbing lithium, Or a metal compound, a layer made of any single element, or a thin film made of a plurality of layers, or (B) a metal simple substance, alloy, or metal compound capable of reversibly occluding and desorbing lithium, And a thin film formed by laminating a total of two or more layers by using both layers of a single metal or an alloy that does not allow lithium to be reversibly occluded / desorbed. The thin film is laminated on the surface of the release layer by a vacuum deposition method or a sputtering method to obtain a laminate, and the thin film is removed from the laminate using a solvent capable of dissolving the resin. Peel off A thin film layer peeling step, a fine grinding step for finely grinding the thin film present in the solvent, and a concentration adjusting step for adjusting the solid content concentration in the solvent of the finely ground thin film after the fine grinding step. It is characterized by being obtained through these.

  Invention of Claim 3 of this invention is the flaky thin film fine powder dispersion of Claim 1 or Claim 2, Comprising: One said flaky thin film fine powder of the said flaky thin film fine powder The average major axis, which is the average value of the entire scale-like thin film fine powder of the longest length from end to end in a substantially plan view, is 0.1 μm to 100 μm, and one scale An average thickness, which is an average value of the entire scale-like thin film fine powder, of the thickness of the thin film fine powder in a substantially side view is 0.01 μm or more and 3 μm or less.

  Invention of Claim 4 of this-application invention is the flaky thin film fine powder dispersion liquid of any one of Claim 1 thru | or 3, Comprising: The said average long diameter of the said flaky thin film fine powder and the said The aspect ratio expressed by the ratio to the average thickness, that is, the average major axis / average thickness is 5 or more.

The invention according to claim 5 of the present invention is the scale-like thin film fine powder dispersion according to any one of claims 1 to 4, wherein the thin film (A) occludes and desorbs lithium. It is a thin film of a single layer or a plurality of layers using any one of the following groups (1) to (3) as a possible substance.
(1) Metal simple substance: silicon, tin, germanium, aluminum, indium, magnesium, calcium, lead, arsenic, antimony, bismuth, silver, gold, zinc, cadmium (2) Alloy: tin-copper alloy (Cu ₅ Sn ₅ ) , Silicon-magnesium alloy (Mg ₂ Si), iron-tin alloy (Sn ₂ Fe), tin-nickel alloy (NixSn), tin-cobalt alloy (CoxSn), silicon-nickel alloy (NiSi), silicon-iron alloy ( FeSi), nickel-magnesium alloy (MgxNi), antimony-tin alloy (SnSb), antimony-indium alloy (InSb), silver-tin-antimony alloy (AgSnSb),
(3) Metal compound: Oxide or sulfide mainly composed of a simple metal shown in (1), or transition metal oxide or sulfide

The invention according to claim 6 of the present invention is the scaly thin film fine powder dispersion according to any one of claims 1 to 4, wherein the thin film occludes and desorbs (B) lithium. One of the following groups shown in (1) to (3) is used as a possible substance, and the group shown in the following (4) to (5) is a substance that does not allow lithium to be absorbed and desorbed. It is characterized by using any of these.
(1) Metal simple substance: silicon, tin, germanium, aluminum, indium, magnesium, calcium, lead, arsenic, antimony, bismuth, silver, gold, zinc, cadmium (2) Alloy: tin-copper alloy (Cu ₅ Sn ₅ ) , Silicon-magnesium alloy (Mg ₂ Si), iron-tin alloy (Sn ₂ Fe), tin-nickel alloy (NixSn), tin-cobalt alloy (CoxSn), silicon-nickel alloy (NiSi), silicon-iron alloy ( FeSi), nickel-magnesium alloy (MgxNi), antimony-tin alloy (SnSb), antimony-indium alloy (InSb), silver-tin-antimony alloy (AgSnSb),
(3) Metal compounds: Oxides or sulfides mainly composed of simple metals shown in (1), or transition metal oxides or sulfides (4) Simple metals: titanium, manganese, iron, nickel, chromium, copper, Zirconium, molybdenum, tantalum, tungsten (5) alloy: an alloy mainly composed of a single metal shown in (4)

  Invention of Claim 7 of this invention is scale-like thin film fine powder dispersion liquid of any one of Claim 1 thru | or 6, Comprising: The said solvent is water or an organic solvent, Features.

  The invention relating to the scaly thin film fine powder according to claim 8 of the present invention has undergone a solvent removal step of removing the solvent in the scaly thin film fine powder dispersion according to any one of claims 1 to 7. It is obtained.

  The invention relating to the paste according to claim 9 of the present invention is the flaky thin film fine powder dispersion according to any one of claims 1 to 7, or the flaky thin film fine powder according to claim 8, Any one of the above, a conductive filler, and a binder are mixed together to be obtained.

  The invention according to claim 10 of the present invention is the paste according to claim 9, wherein the conductive filler is highly conductive carbon black, and the binder is polyvinylidene fluoride, carboxymethylcellulose, and alkalis thereof. It is a metal salt, polyacrylic acid and alkali metal salt thereof, or a mixture of a plurality thereof.

  The invention relating to the battery electrode according to claim 11 of the present invention is characterized by being obtained by laminating the paste according to claim 9 or claim 10 on the surface of the current collector.

  A twelfth aspect of the present invention is the battery electrode according to the eleventh aspect, wherein the current collector is one of copper, nickel, and aluminum.

  The invention related to the lithium secondary battery according to claim 13 of the present invention is characterized by using the battery electrode according to any one of claims 10 to 12.

  The invention relating to the lithium secondary battery according to claim 14 of the present invention uses the battery electrode according to any one of claims 10 to 12, and includes an electrode film-forming additive, One or more of a flammable additive, a nonflammable additive, and an overcharge preventing additive are added.

  As described above, since the scaly thin film fine powder dispersion according to the present invention is a substance capable of reversibly occluding and desorbing lithium, if this is used as a negative electrode of a lithium secondary battery, conventional graphite ( The initial charge capacity can be increased as compared with the case where carbon is used for the negative electrode. If this is used as the negative electrode of a lithium secondary battery, the cycle characteristics can be improved as compared with the case where conventional silicon is used for the negative electrode. That is, if this is used as the negative electrode of a lithium secondary battery, the lithium secondary battery can be used repeatedly for a long period of time, that is, the life can be extended. In particular, regarding the shape of the scaly thin film fine powder, the average major axis is 0.1 μm or more and 100 μm or less, and the average thickness is 0.01 μm or more and 3 μm or less. If the electrode obtained by applying it on the surface of the electric conductor is used as the negative electrode of a lithium secondary battery, the life of the lithium secondary battery can be extended while maintaining high silicon capacity compared to conventional lithium secondary batteries. . Moreover, if the aspect ratio of the flaky thin film fine powder is 5 or more, a better flaky thin film fine powder dispersion for a lithium secondary battery negative electrode can be obtained, and further in the electrolyte of the lithium secondary battery. By adding one or more of electrode film forming additives, flame retardant additives, non-flammable additives, overcharge prevention additives, it is possible to further extend the life of lithium secondary batteries. In addition, some lithium secondary batteries have the characteristics that some additives can increase flame retardancy and incombustibility, prevent accidents due to overcharging, and more reliably prevent electrode dusting. It is done.

  In short, by using the scaly thin film fine powder contained in the scaly thin film fine powder dispersion according to the present invention, damage due to distortion due to expansion and contraction of the negative electrode using silicon, which has been considered a problem in the conventional lithium secondary battery, can be obtained. As a result, it is easy to obtain a negative electrode that realizes a lithium secondary battery having high cycle characteristics while maintaining high capacity of silicon.

  Further, as a method for obtaining a scaly thin film fine powder dispersion or a scaly thin film fine powder according to the present invention, a laminate having a structure of base film / peeling layer / thin film layer is prepared, and this peeling is then performed. The present invention uses a method in which a thin film layer is peeled from a laminate while using a solvent in which the layer can be dissolved, and then the peeled thin film layer present in the solvent is finely pulverized. It can be said that such a scaly thin film fine powder dispersion can be easily obtained.

It is typical sectional drawing for demonstrating an example of the negative electrode produced in the Example of this invention. (A)-(f) is a conceptual schematic diagram for demonstrating a suitable example of the negative electrode fine powder of this invention. It is a block diagram for demonstrating an example of the lithium secondary battery produced in the Example of this invention.

  Embodiments of the present invention will be described below. The embodiment shown here is merely an example, and is not necessarily limited to this embodiment.

(Embodiment 1)
A scaly thin film fine powder dispersion (hereinafter also simply referred to as “dispersion”) according to the present invention will be described as a first embodiment.

  The dispersion according to the present embodiment is a liquid in which a thin film finely pulverized in a solvent exists as a thin film fine powder, if necessary. Moreover, it can be said that the shape of each thin-film fine powder has the characteristic in that it is scaly by simply pulverizing the thin film. It should be noted in advance that the dispersion according to the present embodiment is supposed to be finally used for the negative electrode of a lithium secondary battery.

First, the dispersion according to this embodiment will be described.
The dispersion according to the present embodiment includes a scaly thin film fine powder (hereinafter also simply referred to as “fine powder”) obtained by finely pulverizing a metal simple substance, an alloy, or a thin film of a metal compound in a solvent. A dispersion for use in an electrode of a lithium secondary battery. The simple metal, alloy, or metal compound used as the fine powder is a substance that can reversibly store and desorb lithium.

First, the scaly thin film fine powder will be described.
In the present embodiment, the scaly thin film fine powder is obtained by finely pulverizing a thin film made of any one of a metal, an alloy, and a metal compound. Even if is selected, the substance is a substance capable of occluding and desorbing lithium. There are various kinds of such substances, and examples include the following.

That is,
(1) Examples of simple metals include silicon, tin, germanium, aluminum, indium, magnesium, calcium, lead, arsenic, antimony, bismuth, silver, gold, zinc, cadmium, etc.
(2) As an alloy, tin-copper alloy (Cu ₅ Sn ₅ ), silicon-magnesium alloy (Mg ₂ Si), iron-tin alloy (Sn ₂ Fe), tin-nickel alloy (NixSn), tin-cobalt alloy (CoxSn), silicon-nickel alloy (NiSi), silicon-iron alloy (FeSi), nickel-magnesium alloy (MgxNi), antimony-tin alloy (SnSb), antimony-indium alloy (InSb), silver-tin-antimony alloy (AgSnSb), etc.
Further, (3) a metal compound, which is an oxide or sulfide mainly composed of a single metal shown in (1), or a transition metal oxide or sulfide, etc.
Can be considered.

  In the following description of the present embodiment, it is assumed that a silicon thin film made of silicon alone is finely pulverized.

  The shape of the thin film fine powder obtained by finely pulverizing the silicon thin film in the present embodiment is basically scaly, and a method for obtaining a dispersion containing the fine powder will be described later.

Here, the average thickness and average major axis of the shape of the scaly thin film fine powder will be described.
The fine powder according to the present embodiment literally has a scaly appearance. In other words, each is in the form of a very fine powder, but almost all of them have a scaly appearance when observed individually. This is because it is obtained by finely pulverizing the thin film, and naturally, the crushed individual substances are flat.

  Further observation of the individual scaly powders reveals that the length from end to end is quite different from one end to another in a substantially plan view. The average value in the maximum length of the scaly fine powder, that is, the average major axis that is the average value of the length from end to end, and considering the range of suitable values in the present embodiment, In such a scaly thin film fine powder, it is preferably 0.1 μm or more and 100 μm or less.

  Also, the thickness of the scale-like metal fine powder in a side view is naturally different in thickness, and even if it is a single metal fine powder, if it is enlarged and observed, it has a completely uniform thickness. However, the average thickness obtained by averaging the individual thicknesses is preferably 0.01 μm or more and 3 μm or less in the present embodiment.

  Then, if the flaky thin film fine powder has an aspect ratio, that is, an average major axis / average thickness of 5 or more, more preferably 10 or more, the shape of the flaky thin film fine powder is the same as that of the present embodiment. It means having a preferred flat shape in the form.

  The reason why the numerical ranges of the average major axis, the average thickness, and the aspect ratio are preferably as described above will be separately described later.

  As described above, in this embodiment, by defining the numerical ranges relating to the average major axis, average thickness, and aspect ratio of the scaly thin film fine powder, an appropriate size that is neither too small nor too large as necessary. The scaly thin film is fine powder.

  The average major axis and the average thickness of the metal fine powder described above were determined by the following method. It should be noted that the present invention is not limited to this embodiment, and all the same is true in the present invention.

  First, the average major axis was measured using a laser diffraction / scattering particle size distribution analyzer, and the 50% average particle diameter (median diameter) obtained as a result was taken as the average major axis.

  In addition, the average thickness is the thickness of the laminar thin film fine powder as it is in the laminating method used when producing the dispersion according to the present embodiment described later. As a thickness measurement, a plurality of laminated portions were measured by a fluorescent X-ray analyzer, and a value obtained as an average value was taken as an average thickness.

The scale-like thin film fine powder dispersion described above is obtained as follows.
First, a release layer made of a resin is laminated on the surface of a polymer resin film that is a base film.

  Next, as described above, the layer made of any one of a simple substance, an alloy, or a metal compound capable of reversibly occluding and desorbing lithium as a thin film, that is, in this embodiment, silicon is vacuum-deposited, or A laminate manufacturing process is performed in which a laminate is obtained by laminating the surface of the release layer by a so-called dry coating method such as sputtering.

  Next, the thin film layer peeling process which peels a thin film from a laminated body is performed with respect to the obtained laminated body, using the solvent which can dissolve resin which forms the peeling layer mentioned above.

  Then, a fine pulverization step for finely pulverizing the thin film present in the solvent is performed, and then a concentration adjustment step for adjusting the solid content concentration in the solvent of the finely pulverized thin film is performed. A scaly thin film fine powder dispersion for use in a lithium secondary battery electrode according to the embodiment can be obtained.

This procedure will be described.
As the base film, a conventionally known polymer resin film may be used. For example, a polyethylene terephthalate (PET) film, a polypropylene film, a polyamide film, and the like can be considered. Here, a PET film having a thickness of 25 μm is used. . By the way, if it is a PET film, its handling and the like are well known and used because it is easy. Further, the thickness of the PET film is not particularly limited, but a thickness of about 12 μm or more and 100 μm or less is preferable from the viewpoint of operability described below.

  In this embodiment, the base film is not limited to a PET film. For example, if a polymer resin film resistant to a solvent capable of dissolving a release layer described later is used as the base film. For example, since the base film is not dissolved or damaged by the solvent even after the thin film layer peeling step described later, it can be used again as a base film, that is, a reusable base material. It should be noted that it can be used as a film and can be made suitable.

  A release layer is laminated on the surface of the PET film. This release layer must be easily dissolved by a specific solvent in the thin film layer peeling step described later. The thickness of the release layer is not particularly limited as long as it is a level that can be dissolved in a specific solvent as described later. It is not limited. In the present embodiment, it is considered that a release layer that is soluble in an organic solvent such as butyl acetate or water, such as cellulose acetate butyrate (CAB), is suitable. Then, CAB shall be used. This CAB is laminated on the surface of the PET film by a so-called known wet coating method such as a gravure coating method. More specifically, a PET film on which CAB is laminated is obtained by laminating CAB on the PET film by a gravure coating method while conveying the PET film by roll-to-roll.

  The thickness of the release layer by CAB may be set as appropriate. In short, it is not so thin that it does not function sufficiently as a release layer, and is too thick so that it does not adversely affect the thin film layer peeling process described later. It may be set as such a thickness.

  If a film obtained by laminating a release layer made of CAB on the surface of the PET film can be prepared, then a laminate manufacturing process for laminating silicon on the surface of the release layer is performed.

  Here, as a method of laminating silicon, any of a group of conventionally known dry coating methods may be used, but in this embodiment, a vacuum deposition method generally used is used.

  When the silicon is laminated, the thickness of the silicon thin film layer may be 0.01 μm or more and 3 μm or less. This is because, as will be described later, the thin film fine powder in the scaly thin film fine powder dispersion according to the present example is made from the silicon thin film layer laminated in this laminate manufacturing process. That is, the silicon thin film layer is peeled off from the base film and finely pulverized until it becomes a fine powder, whereby a scaly thin film fine powder is obtained. In the obtained scaly thin film fine powder dispersion Since the thickness of the thin film fine powder is desired to be 0.01 μm or more and 3 μm or less, the thickness at the time of first lamination may be set within the above range.

  Next, the thin film layer peeling process which peels a thin film from a laminated body is performed with respect to the obtained laminated body, using the solvent which can dissolve resin which forms the peeling layer mentioned above. In the present embodiment, an organic solvent is used as the solvent, but this may be selected according to the resin forming the release layer, and water may be used as the solvent, for example. In any case, what is necessary is just to select the thing according to the peeling layer used. By passing through this step, a solution in which the thin film peeled in the solvent is obtained.

  Next, a fine pulverization step for finely pulverizing the thin film present in the solvent is performed. The pulverization method in this fine pulverization step is not particularly limited in this embodiment or a special method is selected, and as a result, if the pulverization can be performed so as to satisfy the numerical conditions such as the size of the scale-like thin film fine powder described above. good.

  Further, after that, a concentration adjusting step for adjusting the solid content concentration in the solvent of the finely pulverized thin film is performed. The concentration adjusting method in this concentration adjusting step is not particularly limited or selecting a special method in the present embodiment, and will be described later as a result by a method such as solvent removal by filtration or heating, or addition of a solvent, for example. What is necessary is just to set it as the density | concentration suitable for obtaining the negative electrode of a lithium secondary battery.

  By passing through the above process, the scaly thin film fine powder dispersion liquid used for the lithium secondary battery electrode concerning this Embodiment is obtained. Further, in order to take out the scaly thin film fine powder from such a dispersion, for example, a solvent removal step of removing the solvent, such as removing the solvent by drying the dispersion, is not described in detail here. It should be noted that it can be implemented according to actual use.

  In addition, it is mentioned later about making a lithium secondary battery electrode using the scaly thin film fine powder dispersion liquid obtained by this Embodiment.

(Embodiment 2)
Although the scaly thin film fine powder contained in the scaly thin film fine powder dispersion according to the first embodiment described above is assumed to be a single layer made of silicon alone, a case different from this will now be described. .

  When the scaly thin film fine powder dispersion obtained by the present invention is used for a lithium secondary battery electrode, the fine powder obtained by a thin film that is a single layer of silicon alone is suitably used as the scaly thin film fine powder. In addition to this, a thin film was prepared by laminating two or more different types of materials that can reversibly absorb and desorb lithium. It was found that the same effect as in the case of the first embodiment can be obtained even by pulverized fine powder.

Therefore, this case will be described as a second embodiment.
Since the dispersion obtained by this embodiment is basically the same as that of the first embodiment described above, its description is omitted.

  In the first embodiment, a single layer of silicon is laminated on the surface of the release layer having a structure of base film (PET film) / release layer, and finally, a fine powder is obtained using this. As described above, in the present embodiment, the layer formed on the surface of the release layer is not a single layer but a plurality of layers of two or more layers.

  In the case of this embodiment, the substance to be selected is a substance capable of occluding and desorbing lithium in any layer. There are various kinds of such substances, and examples thereof include the following.

That is,
(1) Examples of simple metals include silicon, tin, germanium, aluminum, indium, magnesium, calcium, lead, arsenic, antimony, bismuth, silver, gold, zinc, cadmium, etc.
(2) As an alloy, tin-copper alloy (Cu ₅ Sn ₅ ), silicon-magnesium alloy (Mg ₂ Si), iron-tin alloy (Sn ₂ Fe), tin-nickel alloy (NixSn), tin-cobalt alloy (CoxSn), silicon-nickel alloy (NiSi), silicon-iron alloy (FeSi), nickel-magnesium alloy (MgxNi), antimony-tin alloy (SnSb), antimony-indium alloy (InSb), silver-tin-antimony alloy (AgSnSb),
Further, (3) a metal compound, an oxide or sulfide mainly comprising a single metal shown in (1), or a transition metal oxide or sulfide,
Can be considered.

  That is, for example, a thin film having a configuration of “silicon / tin” may be laminated on the surface of the release layer having a configuration of “PET film / release layer”, or may be “silicon / tin-copper alloy”, Further, “tin / silicon” or “tin-copper alloy / silicon” may be used. Further, the number of layers may be three, such as “silicon / tin / silicon”, or a plurality of layers may be stacked in the same manner.

  The method of laminating these on the release layer side of the PET film / release layer may be by a conventionally known so-called dry coating method, and is not particularly limited. Here, the laminated thin film will be further described as having a structure of “silicon / tin”.

  However, it is preferable that the average thickness of the layer formed of the thin film of silicon / tin is 0.01 μm or more and 3 μm as in the case of the first embodiment. Similarly, the average major axis of the thin film fine powder obtained by finely pulverizing the thin film layer is preferably 0.1 μm or more and 100 μm or less, and the aspect ratio is also 5 or more, more preferably 10 or more. Shall. That is, even if the layer configuration is changed, the same effect cannot be obtained unless the overall thickness is the same as in the first embodiment. Thus, for example, a combination of “silicon / tin”, in which the thickness of the silicon layer is 2 μm and the thickness of the tin layer laminated thereon is 1 μm, or the silicon layer is 0.1 μm. A combination of a tin layer of 2.5 μm may be used.

  And the dispersion liquid concerning this Embodiment is obtained by implementing the process similar to 1st Embodiment. How to use the obtained dispersion will be described later.

(Embodiment 3)
Further, a dispersion having a configuration different from that of the first embodiment and the second embodiment will be described.

  In the first embodiment, the fine powder is based on a single layer using only one kind of substance capable of reversibly occluding and desorbing lithium such as silicon, and in the second embodiment, for example, silicon / tin. However, in addition to these, the inventor has obtained a plurality of layers obtained by laminating two or more substances capable of reversibly occluding and desorbing lithium. Even if the dispersion liquid is obtained by pulverizing a thin film formed by laminating a material that does not reversibly absorb and desorb lithium simultaneously with a material that can reversibly absorb and desorb lithium, the same effect can be obtained. I found out. In this embodiment, this case will be described. Even in this embodiment, the description of the same parts as those in the first and second embodiments is omitted.

  In the first and second embodiments, the base material film (PET film) / peeling layer is configured such that silicon is laminated as a single layer on the peeling layer side surface, and two or more types of lithium are further added. In the present embodiment, the case where a plurality of substances capable of reversibly occluding and desorbing are stacked has been described. In this embodiment, (A) a substance capable of reversibly occluding and desorbing lithium and (B) lithium Is used to obtain a scaly thin film fine powder dispersion using a thin film in which a substance that cannot be reversibly occluded and desorbed simultaneously.

Here, (A) as a substance capable of reversibly inserting and extracting lithium,
(1) Examples of simple metals include silicon, tin, germanium, aluminum, indium, magnesium, calcium, lead, arsenic, antimony, bismuth, silver, gold, zinc, cadmium, etc.
(2) As an alloy, tin-copper alloy (Cu ₅ Sn ₅ ), silicon-magnesium alloy (Mg ₂ Si), iron-tin alloy (Sn ₂ Fe), tin-nickel alloy (NixSn), tin-cobalt alloy (CoxSn), silicon-nickel alloy (NiSi), silicon-iron alloy (FeSi), nickel-magnesium alloy (MgxNi), antimony-tin alloy (SnSb), antimony-indium alloy (InSb), silver-tin-antimony alloy (AgSnSb),
Further, (3) a metal compound, an oxide or sulfide mainly comprising a single metal shown in (1), or a transition metal oxide or sulfide,
Can be considered.

In addition, (B) as a substance that does not reversibly absorb and desorb lithium,
(4) Metal simple substance: Titanium, manganese, iron, nickel, chromium, copper, zirconium, molybdenum, tantalum, tungsten (5) Alloy: It is considered to use an alloy mainly composed of a metal simple substance shown in (4).

  Hereinafter, when (A) a substance capable of reversibly occluding and desorbing lithium is ◯, and (B) a substance not reversibly occluding and desorbing lithium is x, May be “O / X”, “O / X / O”, “X / O / X”, or “O / O / X”. (Adjacent circles are different) and may be “× / × / ◯”. (The adjacent Xs are different.) In short, the thin film in this embodiment is composed of a plurality of layers, and at least one (A) lithium is reversibly occluded in the plurality of layers. It is characterized by satisfying the condition that a substance that can be desorbed and a substance that cannot reversibly occlude and desorb one or more (B) lithiums are used at the same time. In this embodiment, “silicon / nickel / silicon” is assumed.

  A method for sequentially laminating these substances on the release layer side of the PET film / release layer may be based on a conventionally known so-called dry coating method, and is not particularly limited.

  Also in the present embodiment, as described in the second embodiment, the average thickness of the thin film layer composed of a plurality of layers of silicon / nickel / silicon is 0 as in the first embodiment. It is preferably 0.01 μm or more and 3 μm. This is also the same, but the thickness of each layer should be the above-mentioned total thickness, that is, 0.01 μm or more and 3 μm or less. For example, the thickness of each layer of silicon / nickel / silicon is 0.3 μm, respectively. The thickness of the silicon layer at both ends may be non-uniform such that the thickness of the silicon layer is 0.5 μm and the thickness of the nickel layer is 0.3 μm.

  Similarly, the average major axis of the thin film fine powder obtained by finely pulverizing the thin film layer is also preferably 0.1 μm or more and 100 μm or less, and the aspect ratio is also 5 or more, more preferably sub-10 or more. Shall.

  Then, by performing the same steps as those in the first embodiment, a dispersion having a configuration of “silicon / nickel / silicon” is obtained. How to use the obtained dispersion will be described later.

(Embodiment 4)
As described above, the scaly thin film fine powder dispersion according to the present invention has been described by dividing the scaly thin film fine powder contained therein into three cases. However, the following description will be for any fine powder and dispersion. The explanation will be continued assuming a dispersion obtained by using a thin film made of a single substance of silicon in the first embodiment after having previously refused the same.

  In this dispersion, fine powder is dispersed and present in the solvent used to obtain the dispersion. Therefore, it is possible to remove the solvent in order to obtain the fine powder itself, and the method for removing is not particularly limited. For example, it is conceivable to remove the solvent by heating the entire dispersion, or to remove the solvent by filtering the dispersion.

  In any case, the dispersion according to the present invention is assumed to be used as an electrode of a lithium secondary battery. In the present embodiment, this electrode is obtained and a lithium secondary battery using the electrode is obtained. Explain.

  Prior to this description, the concentration of the dispersion may be a problem when obtaining the electrode. This is because there is a possibility that the electrode can be suitably obtained depending on the amount of the fine powder in the dispersion, or conversely, the electrode cannot be suitably obtained. Therefore, in order to adjust the concentration, a concentration adjustment step for adjusting the solid content concentration in the solvent of the finely pulverized thin film may be performed after the fine pulverization step. It does not use a simple method. In any case, in the present embodiment, the solvent may be adjusted so as to obtain a desired concentration as a result.

  For example, when water is selected as the solvent, it may be possible to concentrate the dispersion by evaporating the water, or to reduce the concentration by adding water. The method for obtaining an electrode for a lithium secondary battery, more specifically, a negative electrode used for a secondary battery, using the dispersion according to the present invention will be described.

  First, in order to obtain a negative electrode for a lithium secondary battery, a current collector must be selected. However, this may be copper, nickel, aluminum, or the like. "Copper foil").

  And it is made a negative electrode by laminating fine powder on the surface of the copper foil as a current collector, but in order to fix the fine powder on the copper foil surface, for example, the paste described below is prepared and this is used. It is preferable to use a method of laminating and fixing the copper foil surface by coating or the like, and this embodiment also does so.

  This paste is obtained by mixing together a dispersion, a conductive filler, and a binder, or a fine powder obtained by removing a solvent from a dispersion, a conductive filler, and a binder. As an example, it is obtained as follows.

  First, the solvent is evaporated from the dispersion using a high-temperature bath at 60 ° C. After evaporating the solvent, it is further transferred to a vacuum dryer at 80 ° C. and dried for about 1 hour to completely evaporate the solvent. Next, the fine powders (= active material) obtained are collected, weighed so that the weight ratio of this to Ketjen black is 75:15, and they are mixed for 15 minutes. On the other hand, what was made into the aqueous solution so that carboxymethylcellulose may become 5 wt% as a binder is prepared. Here, the aqueous carboxymethyl cellulose solution is weighed so that the weight ratio of carboxymethyl cellulose to fine powder is 75:10. And a paste is obtained by mixing a binder and the mixture obtained by the above-mentioned mixing.

  The obtained paste is used by being laminated on the surface of the copper foil as a current collector by coating or the like, but since the conductor filler is contained in the paste, it is necessary to use fine powder when charging / discharging the lithium secondary battery. A circuit is formed in which the inserted / desorbed electrons are conducted to the copper foil and current is supplied to the external load. In addition, in order to bind such conductive filler and fine powder to each other, a binder is also mixed together. In addition to this, the copper foil and fine powder layer, that is, this paste, It also has the purpose of adhering. In addition, the copper foil and fine powder generated during the process of charging and discharging the lithium secondary battery expand and contract, but still maintain the adhesion of the fine powder and the adhesion between the current collector and the fine powder layer. And the purpose of improving the manufacturing process when making a fine powder into a paste, that is, preventing each element from being scattered from the work while it is in powder form.

  As described above, for example, highly conductive carbon black is preferable as the conductive filler that achieves such a purpose, and this is also used in this embodiment. Similarly, as the binder that achieves such a purpose, polyvinylidene fluoride, carboxymethylcellulose or an alkali metal salt thereof, polyacrylic acid and an alkali metal salt thereof, or a mixture thereof may be used. In the embodiment, carboxymethyl cellulose is used as described above. And these are mixed with fine powder and the paste which has viscosity is obtained.

  On the other hand, the copper foil as the current collector is sufficiently dried in advance. And the obtained paste is apply | coated by techniques, such as a doctor blade method, on the dried copper foil surface, and a negative electrode is obtained by performing vacuum drying for a fixed time after that in high temperature environment.

  Specifically, the doctor blade is applied to the copper foil surface, which is a current collector, so as to have a uniform thickness gap with respect to the copper foil surface, and the doctor blade is moved from the gap while moving on the copper foil surface. By extruding the paste, the paste is applied on the copper foil surface so as to have a uniform thickness. Of course, the paste may be applied to the surface of the copper foil by other methods.

  After that, the template is removed from the surface of the copper foil, the paste is applied to the surface, the copper foil is taken out, and this is dried for a predetermined time and under a predetermined condition.

  When the obtained plate is used as a negative electrode of a lithium secondary battery, the cycle characteristics of the lithium secondary battery can be improved as compared with the case where a negative electrode made of a conventional carbon material is used.

  The operation of the negative electrode of the lithium secondary battery thus obtained will be considered and explained.

  Although the operation of the lithium secondary battery is as described at the beginning, it will be briefly described again focusing on the phenomenon that occurs in the negative electrode during the operation.

Generally, a lithium secondary battery has a structure in which a positive electrode and a negative electrode are immersed in an electrolyte solution in which an electrolyte (for example, lithium hexafluorophosphate (LiPF ₆ )) is dissolved. The principle is that charging / discharging can be performed by transferring and receiving charges by movement of lithium between materials of the positive electrode, the negative electrode, and the electrolyte. Here, when the negative electrode desorbs lithium into the electrolyte, the negative electrode simultaneously discharges the charge to the connected positive electrode side. By doing so, charge movement, that is, current is generated, and the battery functions.

  When used for a certain period of time, lithium desorbed from the negative electrode does not exist in the negative electrode, that is, no charge transfer occurs, no current is generated, and as a result, it does not function as a battery.

  When it does not function as a battery, the lithium secondary battery can be used again as a battery by charging. The movement of the lithium secondary battery in the charged state on the negative electrode, contrary to the previous movement, causes electrons to flow from the positive electrode side and simultaneously occludes lithium present in the electrolyte. That is, lithium is desorbed from the negative electrode when acting as a battery. Conversely, during charging, the negative electrode occludes lithium.

  As described above, lithium is always occluded / desorbed in the negative electrode of the lithium secondary battery. Due to this occlusion / desorption, the negative electrode is constantly expanded and contracted. That is, as the lithium is occluded, the negative electrode expands, and when the lithium is desorbed, the negative electrode contracts.

Therefore, the electrode according to this embodiment will be further described in comparison with a conventional example.
Since conventional negative electrodes use carbon, the cycle characteristics are preferable, but the energy density is low. In order to cope with this problem, it has been proposed to use silicon or a silicon-based alloy as a high-capacity negative electrode. However, since the volume change of silicon is severe, the above-mentioned problems, particularly many times, have been satisfied. There is a problem that the negative electrode made of silicon is easily damaged as a result of being unable to withstand expansion and contraction due to repeated discharge, and thus the cycle characteristics of the lithium secondary battery are deteriorated.

  For example, in the case of a negative electrode using a silicon-based alloy, depending on the selected alloy, the volume may expand to about 300% when lithium is completely occluded. Naturally, repeating the cycle of returning to the original state even when lithium is completely desorbed from this state means that the volume repeatedly expands and contracts vigorously, that is, the life of the negative electrode is shortened accordingly. To do. That is, when the raw material of the negative electrode is a conventionally used spherical and flaky silicon simple substance (hereinafter simply referred to as “conventional simple substance”), the lithium occluded therein naturally penetrates from the external surface into the negative electrode. However, since it is a conventional simple substance, it cannot be said that the penetration speed is always fast. However, on the other hand, the negative electrode tries to occlude lithium one after another. As a result, there is a significant difference in the amount of lithium occluded between the negative electrode surface and the inside, that is, a large difference in concentration. When a significant difference in lithium concentration is generated between the surface and the inside of the negative electrode, it can be easily imagined that when the entire negative electrode made of a conventional single element is observed, a large stress that cannot be ignored is applied inside the negative electrode. In this state, when lithium begins to be desorbed this time, a phenomenon occurs in which lithium begins to desorb more and more on the negative electrode surface, but lithium that has penetrated into the inside is not easily desorbed.

  As described above, when the negative electrode is formed of a conventional simple substance, the difference in lithium concentration inside the negative electrode due to insertion and extraction of lithium becomes a difference that cannot be ignored between the negative electrode surface and the inside. If the cycle is repeated in that state, a significant difference occurs in the magnitude and speed of the degree of expansion / contraction between the negative electrode surface and the inside, and as a result, the negative electrode begins to spontaneously collapse, and finally In other words, a phenomenon occurs in which the negative electrode is pulverized and loses its ability.

  However, in the case of the negative electrode according to the present embodiment, first, a dispersion containing the fine powder according to the present invention using silicon is manufactured, and then a paste containing the fine powder is prepared from this. Since it is obtained by a method of stacking on the current collector surface, the obtained negative electrode is difficult to break.

  In other words, even if each fine powder is in an individual fine powder and continually violently expands and contracts, when observed from the whole negative electrode obtained by the paste containing this, the expansion and contraction of the individual fine powder is inside. All are absorbed. More specifically, the use of scaly fine powder enables lithium atoms alloyed from the negative electrode surface to diffuse quickly into the negative electrode, so that there is a difference in concentration between the negative electrode outside and the inside of the conventional negative electrode described above. As a result, even if expansion and contraction are repeated, no large stress is generated inside the negative electrode, that is, the negative electrode is not crushed or pulverized by the stress. In other words, conventional powders used in conventional single bodies are spherical or normal flakes, so there was a problem of having a thickness, whereas in the present invention, they were very thin. It can solve the problems caused by the expansion and contraction.

  In this way, the negative electrode as a whole has sufficient resistance against expansion and contraction due to repeated charging and discharging of a lithium secondary battery, compared to a conventional negative electrode made of a single plate of silicon laminated on the surface of a copper foil. A new negative electrode can be obtained.

  Therefore, the initial charge capacity of the lithium secondary battery can be increased by first using silicon as the negative electrode, and if the negative electrode according to the present embodiment is used as the negative electrode, the initial charge capacity of the lithium secondary battery is consequently increased. Not only can it be high, but it can also easily follow the intense expansion and contraction of the negative electrode that accompanies charging and discharging, so that the cycle characteristics can be improved. That is, the lithium secondary battery can be used over and over again, that is, the life can be extended.

  However, it should be noted that it is not necessary to make the scaly thin film fine powder as fine as possible. When the volume of the single negative electrode is “1”, when the fine powder of the present invention is used instead as the negative electrode, an unnecessary space may be generated depending on how the fine powders are stacked. That is, if the fine powder is filled in the desired specific volume, and as a result, the filling can be completed completely without generating a useless space in the desired specific volume, the filling rate becomes 100%. This is not the case, and a useless space is inevitably produced. And if it is used as a negative electrode of a lithium secondary battery, this filling rate needs to be 40% or more. However, if the average major axis of the fine powder is made larger than a specific value, a large number of the above-mentioned useless spaces are generated. Therefore, it becomes difficult to reach the required filling rate. In addition, when the average major axis of the fine powder itself becomes a certain value or more, there is a time when a paste containing the fine powder is applied, and the end portions of the fine powder overlap each other no matter how flat the coated surface is. As a result, unevenness that cannot be ignored may occur. In other words, the surface of the electrode may cause unacceptable irregularities. Further, if the average major axis of the fine powder becomes smaller than necessary, it becomes difficult to raise the filling rate to a necessary level due to the force acting between the fine powders.

  The average major axis in the present invention will be further described. The surface of the electrode of the lithium ion secondary battery must be as uniform as possible, that is, in the present invention, after applying the paste laminated on the surface of the copper foil. The surface must be as flat as possible. Moreover, the thickness is required to be 1 μm or more and 30 μm or less. Therefore, if the average thickness of the fine particles becomes thicker than a certain value, the fine powder contained in the paste is longer than necessary even if the paste is applied flatly. The surface may be uneven. Therefore, in the present invention, the average major axis is set to 100 μm or less. In other words, if this value is exceeded, the paste cannot be uniformly laminated. On the other hand, if a fine powder having an average major diameter of less than 0.1 μm is used, the above-mentioned filling rate cannot be achieved, and as a result, the battery capacity per volume cannot be improved. .

  Further, it has been found that when the thickness of the fine powder exceeds a certain thickness, as described above, the same phenomenon as described in the case where the conventional simple substance is used as the negative electrode occurs in each fine powder. In other words, even though it is a fine powder that occludes lithium, it expands abruptly beyond the limit and then shrinks rapidly when lithium is desorbed, resulting in a phenomenon that the fine powder itself is further pulverized and loses its function. I found out. If the thickness is less than a certain thickness, the function of occluding and desorbing lithium cannot be exhibited in the first place, and the problem that it becomes very difficult to handle the flaky fine powder that is too thin is also caused.

  The average thickness in the present invention will be further described. As a result of various studies by the inventors, if the average thickness exceeds 3 μm, fine powder itself was observed to be finely pulverized, so the upper limit was set to 3 μm in the present invention. The lower limit of the thickness at which the fine powder itself can be easily handled was 0.01 μm as a result of various studies by the inventors.

  Further, although the average major axis and the average thickness were as described above, it was found that the aspect ratio that affects the shape of the individual fine powder is preferably 5 or more as a result of various studies by the inventors.

  Therefore, in the present invention, the average major axis of the fine powder is 0.1 μm or more and 100 μm or less, the average thickness is 0.01 μm or more and 3 μm or less, and the aspect ratio is 5 or more. Each was considered suitable.

  As described above, the scaly thin film fine powder used is the same as that described in the first embodiment. However, since the same as that described in the second embodiment is used, the description thereof is omitted.

  Furthermore, it is stated that the same thing can be said even when the scaly thin film fine powder described in the third embodiment is used, but this will be briefly described below.

  The fine powder according to the third embodiment is obtained by simultaneously laminating (A) a substance capable of reversibly occluding and desorbing lithium and (B) a substance not capable of reversibly occluding and desorbing lithium. It has the structure which consists of. This is because if a fine powder using only a substance capable of reversibly occluding and desorbing lithium is used, it may become difficult to control the speed at which lithium can be occluded and desorbed. Therefore, as a result, it may be possible that the life of the lithium secondary battery cannot be made so long. Therefore, in order to prevent such a phenomenon from occurring, (A) and (B) are formed into fine powders laminated simultaneously.

  That is, in the case of a negative electrode made of silicon used in a conventional lithium secondary battery, in order to control the occlusion of lithium, silicon that can occlude lithium on the surface of the current collector and a substance that does not occlude (eg, nickel) However, in this case, it is necessary to repeatedly perform the lamination process, and there are problems that many steps are required for manufacturing the negative electrode, which takes time. Further, even if the layers are alternately laminated, the negative electrode is repeatedly expanded and contracted particularly due to the charging / discharging of the lithium secondary battery, so that the negative electrode is eventually damaged. However, in the case of the dispersion described in the third embodiment, from the beginning, each fine powder has (A) a substance capable of reversibly occluding and desorbing lithium and (B) reversibly occluding and desorbing lithium. Since a substance that cannot be separated is contained at the same time, observation of the entire paste containing the substance makes it easy to control the ability of the entire paste to occlude and desorb lithium.

  Naturally, for the same reason as described above, the negative electrode can be made to follow a severe expansion and contraction, so that the lithium secondary battery can be used over and over again. It becomes possible to extend the life.

  It should be noted that, depending on the experiment by researchers, whatever the detailed mechanism, the use of the substance capable of occluding and desorbing lithium in the present invention and the substance other than that, that is, only the substance capable of occluding and desorbing lithium No matter how the scale-like thin film fine powder or the scale-like thin film fine powder obtained by laminating both at the same time, that is, any configuration described in the first to third embodiments is adopted. As a result, it is possible to obtain a lithium secondary battery that can increase the energy density and at the same time can be used over and over again, that is, can have a long life. Let me state.

  By the way, in the lithium secondary battery using the negative electrode described here, a lithium transition metal oxide such as lithium cobaltate is used as the positive electrode as in the conventional case, and the following is used as the electrolyte. It should be noted that it can be cited as suitable.

  Further, it is conceivable that the electrolyte solution of the lithium secondary battery according to the present invention is as follows.

<1> Examples of the nonaqueous electrolyte solvent include (1) cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate;
Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and the like;
Mixed solvent of these two.
(2) a cyclic carbonate,
Ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane,
Mixed solvent of these two.
Etc. are exemplified.

<2> As the solute of the nonaqueous electrolyte, for example, (1) LiXFp
(Wherein X is P, As, Sb, Al, B, Bi, Ga or In;
(When X = P, As, or Sb, p = 6, and when X = Al, B, Bi, Ga, or In, p = 4)
(2) LiCF ₃ SO ₃ ,
_{(3) LiN (C m F} (2m + 1) SO 2) (C n F (2n + 1) SO 2)
(Wherein m and n are each independently an integer of 1 to 4),
_{(4) LiC (ClF (2l} + 1) SO 2) (C m F (2m + 1) SO 2) (C n F (2n + 1) SO 2)
(Wherein, l, m and n are each independently an integer of 1 to 4)
And mixtures thereof.

  As the nonaqueous electrolyte, a gel polymer electrolyte obtained by impregnating a polymer such as polyethylene oxide or polyacrylonitrile with a nonaqueous electrolyte may be used. Furthermore, in order to improve electrode characteristics, cycle characteristics, storage characteristics, etc., various kinds of vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfite (ES), vinyl ethylene carbonate (VEC), etc. It is preferred to add additives.

This point will be further explained.
In lithium secondary batteries, the phenomenon that the electrolyte solvent decomposes on the electrode surface is known, but it is also known that the storage characteristics and cycle characteristics of the lithium secondary battery deteriorate due to this phenomenon. It is in place. Therefore, in order to cope with this problem, a substance capable of forming a film for protecting the electrode is used as an additive, and a small amount thereof is added to the electrolytic solution. This countermeasure is not limited to the case where conventional carbon (graphite) is used as an electrode or a current collector plate. As seen in this embodiment, a metal such as tin or silicon, its oxide, etc. Even when used as an electrode or a current collector, it is effective, and a lithium secondary battery with higher performance can be obtained by performing the same process in this embodiment.

  In addition, in the vicinity of the electrode of the lithium secondary battery, an organic solvent such as ethylene carbonate used in the electrolytic solution is decomposed, and the decomposition product accumulates on the electrode surface and forms a film on the electrode surface. . When the accumulation increases and the film grows, the electric resistance of the film increases, and as a result, the performance as a battery deteriorates.

  Therefore, in order to prevent such a phenomenon, it is preferable to add a small amount of an electrode film forming additive for preventing a film from being formed on the electrode surface in the electrolyte solution of the lithium secondary battery. If an additive is similarly added to the lithium secondary battery according to the embodiment, a lithium secondary battery with better performance can be obtained.

  For example, when VC, FEC, ES, VEC, etc. are added to the electrolytic solution as electrode film forming additives, these small additives are decomposed from organic solvents such as EC, which are usually used in the electrolytic solution of lithium secondary batteries. Because it has an easy nature, it decomposes before the EC decomposes near the electrode and accumulates near the electrode, forming a film, so even if EC decomposes near the electrode, there is a small amount of decomposition products of additives. It is possible to prevent the phenomenon that they accumulate on the electrode and become a film to increase the electrical resistance.

  Furthermore, the inventors have found that the addition of these substances, particularly VC or FEC, can prevent the electrode from being pulverized, which is a problem when silicon or the like is used for the electrode. The same applies to an electrode in a state where fine powder is applied to the electrode surface, which is an electrode in the present invention. That is, by applying fine powder, not only can the electrode be prevented from being pulverized, but also by adding VC or FEC, the electrode can be further prevented from being pulverized. This makes it possible to extend the life of the lithium secondary battery and thus to extend the life of the lithium secondary battery.

  In addition to adding a small amount of additives for the purpose of film formation to prevent the formation of unnecessary films on the electrode surface in this way, in addition to adding a small amount of flame retardant and non-flammable additives to the electrolyte solution By adding a small amount to the lithium secondary battery, flame retardancy and non-flammability are imparted to increase its safety, and by adding an overload prevention additive, the solvent decomposes when charged more than specified. As a result, it is conceivable that gas is generated and the lithium secondary battery is prevented from rupturing, and for that purpose, vinyl sulfone, chloroanisole, 1-methyl-2-pyrrolidone, alkyl sulfoxide, phosphine oxide compound, aluminum tris. (2,4-pentanedionate) derivatives, boric acid alkyl esters, fluorine-containing aliphatic cyclic compounds, etc. are used as additives. Since it is equivalent to be made to the lithium secondary battery, which more in detail will be omitted here.

  The case where the negative electrode of the lithium secondary battery is obtained by actually using the flaky thin film fine powder dispersion according to the present invention will be further described below with examples, but the present invention is limited to these examples. It is not a thing.

  Further, in the following examples and comparative examples, a test battery (half cell) using a lithium foil as a counter electrode is used, which is a lithium secondary battery using a scaly thin film fine powder dispersion system according to the present invention. This is because the purpose is to evaluate only the negative electrode characteristics of the secondary battery. It should be noted that an actual lithium secondary battery can be obtained by simply substituting the lithium terminal of the counter electrode with a positive electrode made of a lithium transition metal oxide such as cobalt trilithium.

Example 1
A coin battery was manufactured using the negative electrode having the schematic cross-sectional structure shown in FIG.
As a negative electrode fine powder, a silicon single layer fine powder having a film thickness of 100 nm and an average particle diameter of 4.44 μm as shown in FIG. 2A is used, and the weight ratio of the conductive additive ketjen black and the binder carboxymethyl cellulose sodium is respectively. The mixture was mixed using an agate mortar at a ratio of 75:15:10 to prepare a viscous paste. The paste was applied to a copper foil (Φ15 × 0.05 mm) of a current collector that had been ultrasonically cleaned with acetone for about 30 minutes and then dried so as to have a diameter of about 10 mm and a thickness of about 50 μm. Then, the negative electrode was produced by performing vacuum drying at 80 degreeC for 12 hours or more.

A lithium foil having a thickness of 0.5 mm and a diameter of 15 mm was used for the counter electrode.
As the electrolytic solution, a solution obtained by dissolving 1 M (mol / l) of lithium perchlorate in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1 was used.

  As shown in FIG. 3, a coin battery was fabricated using a bipolar coin-type cell, with the working electrode and the counter electrode, and a separator Celgard 2326 sandwiched between the negative electrode and the counter electrode. The cell was assembled in an argon glow box with a circulation device.

(Example 2)
A coin battery was manufactured using the negative electrode having the schematic cross-sectional structure shown in FIG.
As a negative electrode fine powder, a laminated structure in which the upper and lower surfaces of a nickel layer with a film thickness of 30 nm as shown in FIG. 2B are sandwiched between silicon layers with a film thickness of 30 nm is used, and a laminated fine powder with an average particle size of 4.46 μm is used. The mixture was mixed with ketjen black, a conductive additive, and sodium carboxymethylcellulose, a binder, at a weight ratio of 75:15:10, using an agate mortar to prepare a viscous slurry. The above slurry was applied on a copper foil (Φ15 × 0.05 mm) of a current collector that had been ultrasonically cleaned with acetone for about 30 minutes and then dried so as to have a diameter of about 10 mm and a thickness of about 50 μm. Then, the negative electrode was produced by performing vacuum drying at 80 degreeC for 12 hours or more.
A coin battery was assembled in the same manner as in Example 1 below.

(Example 3)
A coin battery was manufactured using the negative electrode having the schematic cross-sectional structure shown in FIG.
As a negative electrode fine powder, a laminated fine powder having a laminated structure in which the upper and lower surfaces of a nickel layer having a thickness of 15 nm as shown in FIG. 2C are sandwiched between silicon layers having a thickness of 30 nm and having an average particle size of 4.47 μm is used. The mixture was mixed with ketjen black, a conductive additive, and sodium carboxymethylcellulose, a binder, at a weight ratio of 75:15:10, using an agate mortar to prepare a viscous slurry. The above slurry was applied on a copper foil (Φ15 × 0.05 mm) of a current collector that had been ultrasonically cleaned with acetone for about 30 minutes and then dried so as to have a diameter of about 10 mm and a thickness of about 50 μm. Then, the negative electrode was formed by performing vacuum drying for 12 hours or more at 80 degreeC.
A coin battery was assembled in the same manner as in Example 1 below.

Example 4
A coin battery was manufactured using the negative electrode having the schematic cross-sectional structure shown in FIG.
As a negative electrode fine powder, a laminated structure in which the upper and lower surfaces of a nickel layer having a thickness of 50 nm as shown in FIG. 2D are sandwiched by silicon layers having a thickness of 50 nm is used, and a laminated fine powder having an average particle size of 4.76 μm is used. The mixture was mixed with ketjen black, a conductive additive, and sodium carboxymethylcellulose, a binder, at a weight ratio of 75:15:10, using an agate mortar to prepare a viscous slurry. The above slurry was applied on a copper foil (Φ15 × 0.05 mm) of a current collector that had been ultrasonically cleaned with acetone for about 30 minutes and then dried so as to have a diameter of about 10 mm and a thickness of about 50 μm. Then, the negative electrode was formed by performing vacuum drying for 12 hours or more at 80 degreeC.
A coin battery was assembled in the same manner as in Example 1 below.

(Example 5)
A coin battery was manufactured using the negative electrode having the schematic cross-sectional structure shown in FIG.
A negative electrode fine powder having a laminated structure in which the upper and lower surfaces of a silicon layer having a film thickness of 60 nm as shown in FIG. 2E are sandwiched by nickel layers having a film thickness of 15 nm and having an average particle diameter of 4.02 μm is used. The mixture was mixed with ketjen black, a conductive additive, and sodium carboxymethylcellulose, a binder, at a weight ratio of 75:15:10, using an agate mortar to prepare a viscous slurry. The above slurry was applied on a copper foil (Φ15 × 0.05 mm) of a current collector that had been ultrasonically cleaned with acetone for about 30 minutes and then dried so as to have a diameter of about 10 mm and a thickness of about 50 μm. Then, the negative electrode was formed by performing vacuum drying for 12 hours or more at 80 degreeC.
A coin battery was assembled in the same manner as in Example 1 below.

(Example 6)
A coin battery was manufactured using the negative electrode having the schematic cross-sectional structure shown in FIG.
As the negative electrode fine powder, a laminated structure having a laminated structure in which the upper and lower surfaces of a copper layer with a thickness of 30 nm as shown in FIG. 2 (f) are sandwiched between silicon layers with a thickness of 30 nm, and an average particle size of 4.56 μm is used. The mixture was mixed with ketjen black, a conductive additive, and sodium carboxymethylcellulose, a binder, at a weight ratio of 75:15:10, using an agate mortar to prepare a viscous slurry. The above slurry was applied on a copper foil (Φ15 × 0.05 mm) of a current collector that had been ultrasonically cleaned with acetone for about 30 minutes and then dried so as to have a diameter of about 10 mm and a thickness of about 50 μm. Then, the negative electrode was formed by performing vacuum drying for 12 hours or more at 80 degreeC.
A coin battery was assembled in the same manner as in Example 1 below.

(Comparative Example 1)
Instead of the negative electrode of Example 1, a negative electrode was formed in the same manner as in Example 1 by using -325 mesh silicon powder (Aldrich) as the working fine powder.
The following was performed in the same manner as in Example 1 to assemble the coin battery.

(Performance evaluation of lithium secondary battery)
The performance evaluation of the lithium secondary battery produced in Examples 1-6 and Comparative Example 1 was conducted under the following conditions, and the performance was evaluated in comparison with the battery of Comparative Example 1. The potentials shown below are based on a lithium foil as a counter electrode.

In the charge / discharge cycle test, charging was started by a constant current-constant voltage charging method (CC-CV mode) 6 hours after the coin battery was assembled. The current value at the time of constant-current charging is that the theoretical capacity of silicon is 418.8 mAh / g, and the rate is C / 6 (current that becomes the theoretical capacity at 6 h based on the capacity calculated from the weight of each working fine powder. Value).
After performing constant current charging with the current value obtained by the above method until the charging potential reached 0.02 V, switching to the constant voltage charging method was performed until the current value became 10 μA or less.
After a 30-minute rest period, the discharge was performed until the cut-off potential reached 1.5V.
The rest period between the subsequent charge and discharge was 30 minutes.

  Table 1 shows the capacity retention rates based on the capacities of the first cycle, the tenth cycle, the 20th cycle, the 30th cycle and the capacities of the first cycle obtained in the charge / discharge cycle test.

  From the results shown in Table 1, in Example 1 using the silicon fine powder having a high aspect ratio produced according to the present invention, the cycle characteristics are better than those in Comparative Example 1 using the -325 mesh silicon fine powder. It was. In Example 2 using fine powder having a laminated structure in which a nickel layer is sandwiched between silicon layers, cycle characteristics better than those of Comparative Example 1 and Example 1 are shown. Good cycle characteristics were also obtained in Example 3 in which the thickness was reduced to 15 nm and Example 4 in which the thickness of both the nickel layer and the silicon layer was increased to 50 nm. In contrast to Example 2, Example 5 using a fine powder having a laminated structure in which a silicon layer is sandwiched between nickel layers also shows better cycle characteristics than Comparative Example 1, and the nickel layer of Example 2 is a copper layer. Also in Example 6 using the fine powder, better cycle characteristics than Comparative Example 1 were shown.

(Example 7)
Of the conditions used in Example 1, the electrolyte solution alone was changed to a solution obtained by dissolving 1M lithium perchlorate in an equivalent solvent mixture of EC and DEC, and 5 wt% of vinylene carbonate (VC) was further added. Other conditions were the same as in Example 1, and a coin battery was assembled.

(Example 8)
Of the conditions used in Example 1, the electrolyte solution was changed to a solution in which 1 M of lithium perchlorate was dissolved in a mixed solvent of EC and DEC, and 5 wt% of fluoroethylene carbonate (FEC) was added. The other conditions were the same as in Example 1, and a coin battery was assembled.

Example 9
Of the conditions used in Example 2, the electrolytic solution alone was changed to a solution obtained by dissolving 1M lithium perchlorate in a mixed solvent of EC and DEC, and 5 wt% of VC was added. A coin battery was assembled in the same manner as in Example 2.

(Example 10)
Of the conditions used in Example 2, the electrolytic solution alone was changed to one in which 1 M lithium perchlorate was dissolved in a mixed solvent of EC and DEC, and 5 wt% of FEC was added. A coin battery was assembled in the same manner as in Example 2.

(Comparative Example 2)
Of the conditions used in Comparative Example 1, the electrolyte solution alone was changed to a solution obtained by dissolving 1M lithium perchlorate in a mixed solvent of equal amounts of EC and DEC, and further added with 5 wt% of VC. A coin battery was assembled in the same manner as in Comparative Example 1.

(Comparative Example 3)
Of the conditions used in Comparative Example 1, the electrolyte solution alone was changed to one in which 1 M lithium perchlorate was dissolved in a mixed solvent of equal amounts of EC and DEC, and further 5 wt% of FEC was added. A coin battery was assembled in the same manner as in Comparative Example 1.

(Evaluation of lithium secondary battery performance)
The performance evaluation of the lithium secondary batteries produced in Examples 7 to 10 and Comparative Examples 2 to 3 was conducted under the following conditions, and the performance was evaluated in comparison with the batteries of Comparative Examples 2 to 3. The potentials shown below are based on a lithium foil as a counter electrode.

In the charge / discharge cycle test, charging was started by a constant current-constant voltage charging method (CC-CV mode) 6 hours after the coin battery was assembled. The current value at the time of constant-current charging is that the theoretical capacity of silicon is 418.8 mAh / g, and the rate is C / 6 (current that becomes the theoretical capacity at 6 h based on the capacity calculated from the weight of each working fine powder. Value).
After performing constant current charging with the current value obtained by the above method until the charging potential reached 0.02 V, switching to the constant voltage charging method was performed until the current value became 10 μA or less.
After a 30-minute rest period, the discharge was performed until the cut-off potential reached 1.5V.
The rest period between the subsequent charge and discharge was 30 minutes.

  Table 2 shows the capacity retention rates based on the capacities of the first cycle, the tenth cycle, the 20th cycle, the 30th cycle and the capacities of the first cycle obtained in the charge / discharge cycle test.

  From the results shown in Table 2, with respect to Examples 7 and 8 in which a fine silicon powder having a high aspect ratio prepared according to the present invention was used and VC and FEC were added as additives, Tables in which no additives were used were used. The cycle characteristics were remarkably improved as compared with Example 1 of 1, and high discharge capacity and capacity maintenance were obtained even after 30 cycles. Further, Examples 9 and 10 in which fine powder having a laminated structure in which a nickel layer is sandwiched between silicon layers and VC and FEC are added as additives are also compared with Example 2 in Table 1 in which no additive is used. As a result, the discharge capacity after 30 cycles was improved, and the same or higher capacity was maintained. On the other hand, Comparative Examples 2 and 3 in which fine powder of −325 mesh silicon is used and VC and FEC are added as additives are improved in cycle characteristics as compared with Comparative Example 1 in Table 1 in which no additives are used. As confirmed, the discharge capacity and capacity maintenance after 30 cycles were lower than those of Examples 7, 8, 9, and 10. That is, it has been found that the effect of adding VC and FEC is particularly high when using a silicon fine powder produced according to the present invention and a fine powder having a laminated structure in which a nickel layer is sandwiched between silicon layers.

(Example 11)
Instead of the negative electrode of Example 1, a negative electrode was formed in the same manner as in Example 1 by using a single-layer fine powder of silicon having a film thickness of 50 nm and an average particle size of 4.19 μm as the negative electrode fine powder. In addition, among the conditions used in Example 1, only the electrolytic solution was changed to a solution in which 1M of lithium hexafluorophosphate was dissolved in an equal mixed solvent of EC and DEC, and other conditions were the same as in Example 1. I assembled a coin battery.

(Example 12)
Instead of the negative electrode of Example 1, a negative electrode was formed in the same manner as in Example 1 by using a single-layer fine silicon powder having a film thickness of 200 nm and an average particle size of 4.79 μm as the negative electrode fine powder. In addition, among the conditions used in Example 1, only the electrolytic solution was changed to a solution in which 1M of lithium hexafluorophosphate was dissolved in an equal mixed solvent of EC and DEC, and other conditions were the same as in Example 1. I assembled a coin battery.

(Example 13)
Of the conditions used in Example 12, the electrolytic solution alone was changed to a solution in which 1M of lithium hexafluorophosphate was dissolved in an equal mixed solvent of EC and DEC, and further 10 wt% of VC was added. The coin battery was assembled under the same conditions as in Example 1.

(Evaluation of lithium secondary battery performance)
The performance evaluation of the lithium secondary batteries produced in Examples 7 to 10 and Comparative Examples 2 to 3 was performed under the conditions described in paragraph 0139, and the performance was evaluated. Table 3 shows the capacity retention rates based on the capacities of the first cycle, the 10th cycle, the 20th cycle, the 30th cycle and the 50th cycle and the capacities of the respective first cycles obtained in the charge / discharge cycle test. .

  From the results shown in Example 11 and Example 12 in Table 3, it was found that good cycle characteristics could be obtained even with silicon fine powders having different aspect ratios if the aspect ratio was 10 or more. Further, in Example 13 in which 10 wt% of VC was added as an additive, the capacity retention rate was 80% or more even after 50 cycles, and was produced according to the present invention by comparison with Example 12 in which no additive was used. It was found to be effective for improving the cycle characteristics of silicon fine powder.

  By producing an electrode based on the scaly thin film fine powder dispersion according to the present invention and using this electrode as the negative electrode of a lithium secondary battery, a lithium secondary battery having a high capacity and good cycle characteristics can be obtained. I can do it.

DESCRIPTION OF SYMBOLS 1 Current collector 2 Fine powder 3 Conductive auxiliary agent 4 Binder 5 100-nm-thick silicon single-layer fine powder 6 30-nm thick silicon layer 7 30-nm thick nickel layer 8 15-nm thick nickel layer 9 50-nm thick Silicon layer 10 50 nm thick silicon layer 11 60 nm thick nickel layer 12 30 nm thick copper layer 13 Negative electrode 14 Lithium foil 15 Separator 16 Polytetrafluoroethylene guide 17 Spring

Claims (14)

(A) a thin film made of a single metal layer, an alloy, or a metal compound capable of reversibly occluding and desorbing lithium;
Or (B) a layer of any one of a simple substance, an alloy, or a metal compound capable of reversibly occluding and releasing lithium, and a simple substance or alloy not capable of reversibly occluding and releasing lithium. Any single layer,
A thin film formed by laminating so as to have a total of two or more layers using both layers
A scale-like thin film fine powder capable of occlusion and desorption of lithium formed by finely pulverizing any one of the above thin films is contained in a solvent, and is used for a lithium secondary battery electrode. Thin film fine powder dispersion. On the surface of the polymer resin film that is the base film,
A release layer made of resin;
(A) a thin film made of a single metal layer, an alloy, or a metal compound capable of reversibly occluding and desorbing lithium;
Or (B) a layer of any one of a simple substance, an alloy, or a metal compound capable of reversibly occluding and releasing lithium, and a simple substance or alloy not capable of reversibly occluding and releasing lithium. Any single layer,
A thin film formed by laminating so as to have a total of two or more layers using both layers
A laminate manufacturing process for obtaining a laminate by laminating any one of the above thin films on the surface of the release layer by vacuum deposition or sputtering,
A thin film layer peeling step of peeling the thin film from the laminate while using a solvent capable of dissolving the resin;
A fine grinding step for finely grinding the thin film present in the solvent;
After the fine pulverization step, a concentration adjustment step of adjusting the solid content concentration in the solvent of the finely pulverized thin film;
To be obtained through
A scaly thin film fine powder dispersion for use in a lithium secondary battery electrode. The scaly thin film fine powder dispersion according to claim 1 or 2,
Of the scaly thin film fine powder,
The average major axis, which is the average value of the entire scale-like thin film fine powder, of the longest length among the lengths from end to end in a substantially plan view of one piece of the scale-like thin film fine powder is 0.1 μm or more and 100 μm. And
An average thickness that is an average value of the entire scale-like thin film fine powder of the thickness of one scale-like thin film fine powder in a substantially side view is 0.01 μm or more and 3 μm or less;
A scaly thin film fine powder dispersion characterized by The scaly thin film fine powder dispersion according to any one of claims 1 to 3,
The ratio of the average major axis to the average thickness of the scaly thin film fine powder, that is, the aspect ratio represented by the average major axis / average thickness is 5 or more,
A scaly thin film fine powder dispersion characterized by The scaly thin film fine powder dispersion according to any one of claims 1 to 4,
The thin film is a thin film of a single layer or a plurality of layers using any one of the following groups (1) to (3) as a substance capable of inserting and extracting lithium (A):
A scaly thin film fine powder dispersion characterized by
(1) Metal simple substance: silicon, tin, germanium, aluminum, indium, magnesium, calcium, lead, arsenic, antimony, bismuth, silver, gold, zinc, cadmium (2) Alloy: tin-copper alloy (Cu ₅ Sn ₅ ) , Silicon-magnesium alloy (Mg ₂ Si), iron-tin alloy (Sn ₂ Fe), tin-nickel alloy (NixSn), tin-cobalt alloy (CoxSn), silicon-nickel alloy (NiSi), silicon-iron alloy ( FeSi), nickel-magnesium alloy (MgxNi), antimony-tin alloy (SnSb), antimony-indium alloy (InSb), silver-tin-antimony alloy (AgSnSb),
(3) Metal compound: Oxide or sulfide mainly composed of a simple metal shown in (1), or transition metal oxide or sulfide The scaly thin film fine powder dispersion according to any one of claims 1 to 4,
The thin film (B) uses any one of the following groups (1) to (3) as a substance capable of occluding and desorbing lithium, and is not capable of occluding and desorbing lithium. Using any of the following groups (4) to (5):
A scaly thin film fine powder dispersion characterized by
(1) Metal simple substance: silicon, tin, germanium, aluminum, indium, magnesium, calcium, lead, arsenic, antimony, bismuth, silver, gold, zinc, cadmium,
(2) Alloy: Tin-copper alloy (Cu ₅ Sn ₅ ), silicon-magnesium alloy (Mg ₂ Si), iron-tin alloy (Sn ₂ Fe), tin-nickel alloy (NixSn), tin-cobalt alloy (CoxSn) ), Silicon-nickel alloy (NiSi), silicon-iron alloy (FeSi), nickel-magnesium alloy (MgxNi), antimony-tin alloy (SnSb), antimony-indium alloy (InSb), silver-tin-antimony alloy (AgSnSb) ),
(3) Metal compounds: Oxides or sulfides mainly composed of simple metals shown in (1), or transition metal oxides or sulfides (4) Simple metals: titanium, manganese, iron, nickel, chromium, copper, Zirconium, molybdenum, tantalum, tungsten (5) alloy: an alloy mainly composed of a single metal shown in (4) The scaly thin film fine powder dispersion according to any one of claims 1 to 6,
The solvent is water or an organic solvent;
A scaly thin film fine powder dispersion characterized by It is obtained through a solvent removal step of removing the solvent in the scaly thin film fine powder dispersion according to any one of claims 1 to 7.
A scaly thin film fine powder characterized by Any one of the flaky thin film fine powder dispersion according to any one of claims 1 to 7, or the flaky thin film fine powder according to claim 8, a conductive filler, a binder, Obtained by mixing together,
Characterized by a paste. The paste according to claim 9,
The conductive filler is highly conductive carbon black;
The binder is any one or a mixture of polyvinylidene fluoride, carboxymethylcellulose and alkali metal salts thereof, polyacrylic acid and alkali metal salts thereof,
Characterized by a paste. Obtained by laminating the paste according to claim 9 or 10 on the surface of the current collector,
A battery electrode. The battery electrode according to claim 11,
The current collector is any one of copper, nickel, and aluminum;
A battery electrode. Using the battery electrode according to any one of claims 10 to 12,
A lithium secondary battery. Using the battery electrode according to any one of claims 10 to 12,
In addition, an electrode film-forming additive, a flame retardant additive, a non-flammable additive, an overcharge prevention additive, or a mixture of any or more of them in the electrolyte solution,
A lithium secondary battery.

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