JP2008084842A - Separator for nonaqueous secondary battery, its manufacturing method, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for a lithium secondary battery realizing a nonaqueous electrolyte secondary battery having high initial charge discharge efficiency and good cycle retentivity, and easy in handling, to provide the manufacturing method of the separator and to provide the lithium secondary battery. <P>SOLUTION: Lithium powder stabilized by applying an organic compound or an inorganic compound to the surface is adhered and fixed to the surface of the separator. Loadings of metallic lithium powder are the suitable amount compensating for the irreversible capacity calculated from the initial efficiency of a negative electrode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a separator for a non-aqueous secondary battery and a method for manufacturing the same, and a non-aqueous electrolyte secondary battery, and more particularly to a separator for a lithium ion secondary battery, a method for manufacturing the same, and a lithium ion secondary battery. .

In recent years, the use of lithium ion secondary batteries having a high energy density as portable power sources for notebook computers, mobile phones, and digital cameras is increasing. Lithium ion secondary batteries are also being studied as a power source for electric vehicles that are expected to be put into practical use as environmentally friendly vehicles.
In conventional lithium ion secondary batteries, a carbon material has been used as a negative electrode active material, but a metal that can be alloyed with lithium, such as silicon, which can be expected to have a high charge / discharge capacity due to a recent demand for capacity enhancement, and It is considered to use these oxides as a negative electrode active material. However, when such an alloying metal is used as an active material, high capacity can be expected, but lithium in the positive electrode material is introduced into the negative electrode material for the first charge, and all lithium cannot be taken out by discharge. Therefore, lithium becomes an irreversible cause of being fixed in the negative electrode. As a result, there is a problem that the discharge capacity of the entire battery is reduced and the battery capacity is reduced.

As a measure for solving this problem, a method of previously including a lithium source in the negative electrode material has been proposed. As a form of the lithium source, lithium metal powder (Patent Document 1: JP-A-5-67468), lithium metal foil (Patent Document 2: JP-A-11-86847, Patent Document 3: JP-A-2004-303597) And JP-A-2005-85508) and lithium compounds (Patent Document 5: Patent No. 3287376, Patent Document 6: JP-A-9-283181).
However, these methods have various problems in industrialization, for example, because the production process has a problem in safety and the work in an environment where lithium does not react is complicated.

JP-A-5-67468 Japanese Patent Laid-Open No. 11-86847 JP 2004-303597 A JP-A-2005-85508 Japanese Patent No. 3287376 JP-A-9-283181

  The present invention has been made in view of the above circumstances, and enables a non-aqueous secondary battery having high initial efficiency and excellent cycle retention, and also has good handleability and a method for producing the same. And a non-aqueous electrolyte secondary battery.

  As a result of intensive studies to achieve the above object, the present inventors have found a method that can be easily handled at a dew point of about minus 40 ° C. and completed the present invention. That is, by using a non-aqueous secondary battery separator having a metal lithium powder with a stabilized surface on its surface, it is possible to compensate for irreversible lithium that is fixed in the negative electrode, and the battery capacity is improved. I found.

Accordingly, the present invention provides the following non-aqueous secondary battery separator, a method for producing the same, and a non-aqueous electrolyte secondary battery.
Claim 1:
A separator for a non-aqueous secondary battery having lithium powder on the surface.
Claim 2:
The separator for a non-aqueous secondary battery according to claim 1, wherein the lithium powder is a metallic lithium powder having a surface stabilized.
Claim 3:
The separator for a non-aqueous secondary battery according to claim 1 or 2, wherein a lithium powder having adhesiveness on the surface is adhesively fixed to the separator.
Claim 4:
The separator to which the lithium powder is adhesively fixed is obtained by transferring the tackified lithium powder adhesively fixed to the substrate having releasability to the separator and transferring it to the separator side. The separator for non-aqueous secondary batteries according to claim 3.
Claim 5:
The nonaqueous electrolyte secondary battery using the separator of any one of Claims 1 thru | or 4.
Claim 6:
A separator according to any one of claims 1 to 4, a negative electrode using a negative electrode active material containing silicon and / or silicon oxide capable of occluding and releasing lithium ions, and occluding and absorbing lithium ions. A non-aqueous electrolyte secondary battery comprising: a positive electrode using a positive electrode active material containing a lithium composite oxide or sulfide that can be released; and a non-aqueous electrolyte containing a lithium salt.
Claim 7:
A non-aqueous two-sided lithium powder having a lithium powder on the surface is characterized in that the lithium powder imparted with adhesiveness is adhesively fixed to a substrate having releasability and then brought into contact with a separator to transfer the lithium powder to the separator side. Manufacturing method of separator for secondary battery.

  According to the present invention, a non-aqueous electrolyte secondary battery with high initial efficiency and high cycle retention can be obtained.

Hereinafter, the present invention will be described in detail.
The separator for a non-aqueous secondary battery of the present invention is one in which lithium powder is present on the separator surface, and the non-aqueous electrolyte secondary battery of the present invention using a separator having lithium powder on such a surface is Separator, negative electrode using negative electrode active material containing silicon and / or silicon oxide capable of occluding and releasing lithium ions, and lithium composite oxide or sulfide capable of occluding and releasing lithium ions A positive electrode using a positive electrode active material containing a product, and a non-aqueous electrolyte containing a lithium salt.

  In the non-aqueous electrolyte secondary battery of the present invention, the lithium metal powder on the separator surface elutes into the electrolyte during repeated charging and discharging, resulting in a doped form in the negative electrode. Used to supplement the capacity. Since the metallic lithium powder on the surface of the separator is used to supplement the irreversible capacity of the negative electrode, it is desirable that the amount added is not more than an amount sufficient to supplement the irreversible capacity of the negative electrode. The optimal amount of metallic lithium powder added varies depending on the amount and material of the negative electrode active material, and the irreversible capacity decreases with the amount of addition, but if too much, lithium is deposited on the negative electrode, conversely the battery capacity. Disappears. Therefore, it is preferable to determine the optimum amount of lithium added after obtaining the initial efficiency of the negative electrode separately.

  Although the metal lithium powder concerning this invention is not specifically limited, Since it can apply | coat thinly and uniformly, a thing with an average particle diameter of 0.1-50 micrometers, especially 1-10 micrometers is used suitably.

In the present invention, the average particle diameter can be determined as, for example, the cumulative weight average value D ₅₀ (or median diameter) in a particle size distribution measuring apparatus using a technique such as laser light diffraction.

Moreover, it is preferable to use stabilized lithium powder as the metal lithium powder. By stabilizing the lithium powder, alteration of the lithium powder does not proceed even in a dry room having a dew point of about -40 ° C. Here, the stabilization treatment of the lithium powder is a material whose surface is excellent in environmental stability, for example, organic rubber such as NBR (nitrile butadiene rubber) and SBR (styrene butadiene rubber), EVA (ethylene vinyl alcohol copolymer resin). Or an inorganic compound such as a metal carbonate such as Li ₂ CO ₃ . Moreover, as such a stabilized lithium powder, a commercially available product can be used, and examples thereof include SLMP manufactured by FMC.

  The separator containing lithium powder on the surface is used between the positive electrode and the negative electrode, and the material is not particularly limited as long as it has excellent liquid retention, but in general, a polyolefin such as polyethylene or polypropylene is used. A porous sheet or a nonwoven fabric is mentioned.

  As a method for incorporating the lithium powder on the surface of the separator, a method is preferred in which tackiness is imparted to the surface of the lithium powder, particularly the stabilized lithium powder, and then the lithium powder is brought into contact with the separator to be adhesively fixed. As a method for imparting adhesiveness to the surface of the lithium powder, the lithium powder is immersed in an adhesive substance to coat the surface with the adhesive substance, and then the lithium powder is taken out from the adhesive substance. The amount of coating on the surface varies depending on the adhesive force of the adhesive substance, but after the adhesive is fixed to the surface of the separator, it is sufficient to apply an adhesive force that does not leave the separator surface during the manufacturing process. If the coating amount on the surface is too much than necessary, not only will it take time to dissolve in the electrolyte solution, but the dissolved adhesive substance may hinder battery performance. More specifically, the coating amount of the adhesive substance on the lithium powder is usually 0.01 to 10% by mass, and particularly preferably about 0.1 to 5% by mass.

  As an adhesive substance, a hot-melt type adhesive is used in addition to a general acrylic adhesive, rubber adhesive, and silicone adhesive, but it can be dissolved in a component of an electrolytic solution. preferable.

  When the lithium powder is immersed in the adhesive substance, if the adhesive substance diluted with an organic solvent is used, the surface can be easily uniformly coated and the amount of coating can be easily controlled.

  In order to adhere and fix lithium powder immersed in an adhesive substance, particularly an adhesive substance diluted with a solvent, to a separator, first, a lithium powder immersed in the adhesive substance on the surface of a substrate having releasability is coated with a coater. Apply uniformly by a method or spray method. Thereafter, the solvent used for dilution is removed by drying. Next, a method in which the base material surface having lithium powder and the separator are pressure-bonded to transfer the lithium powder from the base material surface to the separator surface is preferable.

  In the case of using a hot-melt type pressure-sensitive adhesive, it is necessary to heat the base material surface having lithium powder to a predetermined temperature to express the pressure-sensitive adhesiveness.

  As the base material having releasability, a polyethylene terephthalate (PET) film, a polypropylene (PP) film, a paper laminated with polyethylene, and the like coated with a silicone release agent can be used.

  When the mold release property of the base material having the mold release property used is insufficient, the lithium powder is difficult to move to the separator surface when pressure-bonded to the separator. On the contrary, if the release property of the base material is better than necessary, the lithium powder may be detached from the base material in the step of bonding to the separator.

Examples of the positive electrode active material used in the non-aqueous electrolyte secondary battery according to the present invention include oxides or sulfides that can occlude and release lithium ions, and any one or more of these can be used. Is used. Specifically, for example, a metal sulfide or oxide containing no lithium such as TiS ₂ , MoS ₂ , NbS ₂ , ZrS ₂ , VS ₂ or V ₂ O ₅ , MoO ₃ and Mg (V ₃ O ₈ ) ₂ , or lithium composite oxide is exemplified containing lithium and a composite metal such as NbSe ₂ can also be mentioned. Among these, in order to increase the energy density, a lithium composite oxide mainly composed of Li _x MetO ₂ is preferable. Specifically, Met is preferably at least one of cobalt, nickel, iron and manganese, and x is a positive number and is usually a value in the range of 0.05 ≦ x ≦ 1.10. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , Li _x Ni _y Co _1-y O ₂ having a layer structure (where x is the same as above, y is 0 <y <1 in the range)), spinel-structured LiMn ₂ O ₄ and orthorhombic LiMnO ₂ . Furthermore, a substituted spinel manganese compound LiMet _x Mn _1-x O ₄ (where x is a positive number in the range of 0 <x <1) is also used as a high-voltage compatible type. In this case, Met Includes titanium, chromium, iron, cobalt, copper and zinc.

  The lithium composite oxide is obtained by, for example, grinding lithium carbonate, nitrate, chloride or hydroxide and transition metal carbonate, nitrate, oxide or hydroxide according to a desired composition. It is prepared by mixing and baking at a temperature in the range of 600 to 1,000 ° C. in an oxygen atmosphere.

  Furthermore, an organic substance can also be used as the positive electrode active material. Illustrative examples include polyacetylene, polypyrrole, polyparaphenylene, polyaniline, polythiophene, polyacene, polysulfide compound and the like.

Examples of the negative electrode active material used in the non-aqueous electrolyte secondary battery according to the present invention include an active material containing silicon capable of inserting and extracting lithium ions. Specifically, after cleaning with high-purity silicon powder with a metal impurity concentration of 1 ppm or less, hydrochloric acid, and then treating with hydrofluoric acid and a mixture of hydrofluoric acid and nitric acid, a chemical grade of metal grade is removed. Silicon powder, metallurgically refined metal silicon processed into powder, alloys thereof, lower oxides and partial oxides of silicon, silicon nitrides and partial nitrides, and further conducting them For this reason, it includes a material mixed with a carbon material, alloyed by mechanical alloying or the like, a material coated with a conductive agent such as metal by sputtering or plating, and a material in which carbon is precipitated with an organic gas. These active materials have a charge / discharge capacity higher than that of conventionally used graphite. However, a certain amount of lithium introduced into the negative electrode material by the first charge remains in the negative electrode without being taken out by discharge. In particular, silicon oxide, which is a lower oxide of silicon, exhibits excellent cycle characteristics. However, the irreversible capacity of lithium is large and has a problem in practical use. This problem is solved by using the separator having the above, and the active material containing silicon, particularly silicon, silicon oxide represented by SiO _x (0.6 ≦ x <1.6), and silicon fine particles such as silicon dioxide. Particles having a composite structure dispersed in the silicon compound, those covered with a conductive film such as carbon, and the like are suitably used as the negative electrode active material.

  There is no restriction | limiting in particular about the preparation methods of a positive electrode and a negative electrode. In general, an active material, a binder, a conductive agent or the like is added to a solvent to form a slurry, which is applied to a current collector sheet, dried and pressed.

  Examples of the binder used in the non-aqueous electrolyte secondary battery according to the present invention generally include polyvinylidene fluoride, polytetrafluoroethylene, styrene / butadiene rubber, isoprene rubber, various polyimide resins, and the like.

  Examples of the conductive agent used in the non-aqueous electrolyte secondary battery according to the present invention generally include carbon materials such as graphite and carbon black, and metal materials such as copper and nickel.

  Examples of the current collector used in the non-aqueous electrolyte secondary battery according to the present invention include aluminum for the positive electrode or an alloy thereof, and for the negative electrode, a metal such as copper, stainless steel, nickel, or an alloy thereof. .

The nonaqueous electrolytic solution of the present invention contains an electrolyte salt and a nonaqueous solvent. Examples of the electrolyte salt include light metal salts. Light metal salts include alkali metal salts such as lithium salts, sodium salts, or potassium salts, alkaline earth metal salts such as magnesium salts or calcium salts, or aluminum salts. Selected. For example, in the case of a lithium salt, LiBF ₄ , LiClO ₄ , LiPF ₆ , LiAsF ₆ , CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, C ₄ F ₉ SO ₃ Li, CF ₃ CO ₂ Li, ( CF ₃ CO ₂ ) ₂ NLi, C ₆ F ₅ SO ₃ Li, C ₈ F ₁₇ SO ₃ Li, (C ₂ F ₅ SO ₂ ) ₂ NLi, (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) NLi , (FSO ₂ C ₆ F ₄ ) (CF ₃ SO ₂ ) NLi, ((CF ₃ ) ₂ CHOSO ₂ ) ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, (3,5- (CF ₃ ) ₂ C ₆ F ₃ ) ₄ BLi, LiCF ₃ , LiAlCl _4, or C ₄ BO ₈ Li may be used, and any one or two of these may be used in combination.

  The concentration of the electrolyte salt in the nonaqueous electrolytic solution is preferably 0.5 to 2.0 mol / L from the viewpoint of electrical conductivity. The conductivity of the electrolyte at 25 ° C. is preferably 0.01 S / m or more, and is adjusted by the type of electrolyte salt or its concentration.

The solvent for non-aqueous electrolyte used in the present invention is not particularly limited as long as it can be used for non-aqueous electrolyte. Generally, aprotic high dielectric constant solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, dipropyl carbonate, diethyl ether, tetrahydrofuran, 1,2, -Aprotic low viscosity such as acetate ester or propionate ester such as dimethoxyethane, 1,2-diethoxyethane, 1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole, methyl acetate A solvent is mentioned. It is desirable to use these aprotic high dielectric constant solvents and aprotic low viscosity solvents in combination at an appropriate mixing ratio. Furthermore, ionic liquids using imidazolium, ammonium, and pyridinium type cations can be used. The counter anion is not particularly limited, and examples thereof include BF ₄ ⁻ , PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ^{− and the} like. The ionic liquid can be used by mixing with the aforementioned non-aqueous electrolyte solvent.

  In the case of a solid electrolyte or gel electrolyte, it is possible to contain silicone gel, silicone polyether gel, acrylic gel, acrylonitrile gel, poly (vinylidene fluoride) and the like as a polymer material. These may be polymerized in advance or may be polymerized after injection. These can be used alone or as a mixture.

  Furthermore, you may add various additives in the non-aqueous electrolyte of this invention as needed. For example, vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4-vinylethylene carbonate and the like for the purpose of improving cycle life, biphenyl, alkylbiphenyl, cyclohexylbenzene, t-butylbenzene, diphenyl ether for the purpose of preventing overcharge, Examples include benzofuran, various carbonate compounds for the purpose of deoxidation and dehydration, various carboxylic acid anhydrides, various nitrogen-containing compounds, and sulfur-containing compounds.

  The shape of the non-aqueous electrolyte secondary battery according to the present invention is arbitrary and is not particularly limited. In general, a coin type in which an electrode punched into a coin shape and a separator are stacked, a cylinder type in which an electrode sheet and a separator are spiraled, and the like can be given.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to the following Example. In the following examples,% indicates mass%.

[Example 1]
[Preparation of separator with lithium powder adhesively fixed on the surface]
Silicone pressure-sensitive adhesive KR-101 (manufactured by Shin-Etsu Chemical Co., Ltd.) was diluted with toluene so as to have a solid content of 0.1% to obtain 1,000 mL of a pressure-sensitive adhesive treatment solution. In this, 10 g of stabilized lithium powder (manufactured by FMC) with an average particle diameter of 20 μm was immersed and stirred for 10 minutes.
Using a PET film coated with a silicone-based mold release agent X-70-201 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a substrate having releasability, this release surface is treated with an adhesive-treated lithium. The powder was applied by a doctor blade method and dried under reduced pressure to remove toluene.
Next, a lithium powder-containing surface of the obtained base material having releasability and a separator using a polyethylene microporous film having a thickness of 30 μm are pressure-bonded, and the entire amount of the lithium powder of the base material is transferred to the separator surface. A separator having a lithium powder adhered and fixed to the surface was prepared.
From the increase in the mass of the separator before and after the application of the lithium powder, the amount of the lithium powder treated with the adhesive substance was 0.4 mg per 2032 coin-type battery.

[Preparation of negative electrode active material (conductive silicon composite)]
A mixed powder in which silicon dioxide powder and metal silicon powder were mixed at an equimolar ratio was heat-treated in a high-temperature reduced pressure atmosphere at 1,350 ° C. and 0.1 Torr, and the generated SiO gas was deposited in a water-cooled deposition tank. Next, the precipitate was pulverized with a ball mill in hexane to obtain a silicon oxide powder (SiO _x : x = 1.02) having D ₅₀ = 8 μm. The powder obtained here was subjected to X-ray diffraction using Cu-Kα rays, and it was confirmed that the obtained powder was amorphous silicon oxide (SiO _x ) powder. The obtained silicon oxide powder was subjected to thermal CVD at the same time as disproportionation of silicon oxide under a condition of 1,150 ° C. for 2 hours under a methane-argon mixed gas flow using a rotary kiln type reactor. It was collected. The amount of deposited carbon of the obtained black powder was 22.0%, and the obtained black powder was attributed to Si (111) near 2θ = 28.4 °, unlike the silicon oxide powder, from the X-ray diffraction pattern. The size of the crystal is obtained by the Scherrer method from the half width of the diffraction line, and the size of the silicon crystal dispersed in the silicon dioxide is 11 nm. A conductive silicon composite powder in which Si) crystals were dispersed in silicon dioxide (SiO ₂ ) was produced.

[Production of negative electrode]
10% of polyimide is added to the conductive silicon composite powder, and further N-methylpyrrolidone is added to form a slurry. This slurry is applied to a copper foil having a thickness of 20 μm, dried in a vacuum at 80 ° C. for 1 hour, and then subjected to a roller press. Was formed into a negative electrode by vacuum molding at 350 ° C. for 1 hour.

[Production of positive electrode]
As a positive electrode material, a single layer sheet (Pionix Co., Ltd., trade name: Pioxel C-100) using LiCoO ₂ as an active material and an aluminum foil as a current collector was punched into 2 cm ² to obtain a positive electrode.

[Verification of positive and negative electrode capacities in a single cell]
In order to confirm the capacities of the obtained positive electrode and negative electrode, the capacities of the positive electrode and the negative electrode were confirmed with a single battery using lithium as a counter electrode. That is, in a glove box (dew point -80 ° C or lower), metallic lithium, separator, and positive electrode materials and lithium hexafluorophosphate as a non-aqueous electrolyte were mixed in 1/1 (volume ratio) of ethylene carbonate and diethyl carbonate. A 2032 type battery for evaluation was prepared using a non-aqueous electrolyte solution dissolved in a liquid at a concentration of 1 mol / L, and allowed to stand overnight at room temperature. Then, a secondary battery charge / discharge test apparatus (Nagano Co., Ltd.) was prepared. The product was charged at a constant current of 0.5 mA / cm ² until the voltage of the test cell reached 4.2V. The charge capacity at this time was defined as the initial capacity. The discharge was performed at a constant current of 0.5 mA / cm ² , and when the cell voltage dropped below 2.5 V, the discharge was terminated, the discharge capacity was obtained, and the positive electrode capacity was measured. As a result, the charge capacity was 4.6 mAh and the discharge capacity. The positive electrode was 4.5 mAh, initial efficiency 98%, and irreversible capacity 0.1 mAh.
Similarly, each material of metallic lithium, separator, and negative electrode and lithium hexafluorophosphate as a non-aqueous electrolyte are dissolved in a 1/1 (volume ratio) mixture of ethylene carbonate and diethyl carbonate at a concentration of 1 mol / L. The non-aqueous electrolyte solution was used to produce a 2032 type battery for evaluation, and charging was performed at a constant current of 0.5 mA / cm ² until the voltage of the test cell reached 0.005V. The charge capacity at this time was defined as the initial capacity. The discharge was performed at a constant current of 0.5 mA / cm ² , and when the cell voltage exceeded 2.0 V, the discharge was terminated, the discharge capacity was determined, and the negative electrode capacity was measured. As a result, the charge capacity was 6.0 mAh and the discharge capacity. The negative electrode was 4.5 mAh, initial efficiency 75%, and irreversible capacity 1.5 mAh.

[Evaluation of battery performance using lithium-containing separator]
In a glove box (dew point -80 ° C. or lower), a separator in which lithium powder is adhered and fixed to the surface obtained above, a negative electrode, a positive electrode, and lithium hexafluorophosphate as a non-aqueous electrolyte are made of ethylene carbonate and diethyl carbonate. A 2032 type coin battery for evaluation was produced using a non-aqueous electrolyte solution dissolved in a 1/1 (volume ratio) mixture at a concentration of 1 mol / L.
The produced lithium ion secondary battery was allowed to stand at room temperature overnight, and then charged with a secondary battery charge / discharge test apparatus (manufactured by Nagano Co., Ltd.) until the voltage of the test cell reached 4.2V. Charging was performed at a constant current of 5 mA / cm ² . The charge capacity at this time was defined as the initial capacity. Discharging was performed at a constant current of 0.5 mA / cm ² , and when the cell voltage fell below 2.5 V, the discharging was terminated and the discharge capacity was determined. The above charge / discharge test was repeated. The initial charge capacity / discharge capacity ratio (%) is the initial efficiency, and the cycle performance is determined as the ratio of the maximum discharge capacity after several charge / discharge cycles and the discharge capacity after 50 cycles. did. As a result, the initial efficiency was 88% and the cycle retention was 95%.

[Comparative Example 1]
In Example 1, a 2032 type coin battery for evaluation similar to that in Example 1 was prepared except that a 30 μm thick polyethylene microporous film having no lithium powder on the surface was used as a separator. The battery performance was evaluated in the same manner as described above. As a result, the initial efficiency was 72% and the cycle retention was 95%.

[Example 2]
[Preparation of separator with lithium powder adhesively fixed on the surface]
Acrylic pressure-sensitive adhesive BPS-2411 (manufactured by Toyo Ink Co., Ltd.) was diluted with toluene so as to have a solid content of 0.1% to obtain 1,000 mL of a pressure-sensitive adhesive treatment liquid. In this, 10 g of stabilized lithium powder (manufactured by FMC) with an average particle diameter of 20 μm was immersed and stirred for 10 minutes.
Using a PET film coated with a silicone release agent KS-837 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a substrate having releasability, an adhesive substance-treated lithium powder is applied to this release surface, It apply | coated by the doctor blade method and reduced pressure toluene was removed by drying under reduced pressure.
Next, a lithium powder-containing surface of the obtained base material having releasability and a separator using a polyethylene microporous film having a thickness of 30 μm are pressure-bonded, and the entire amount of the lithium powder of the base material is transferred to the separator surface. A separator having a lithium powder adhered and fixed to the surface was prepared.
From the increase in the mass of the separator before and after the application of the lithium powder, the amount of the lithium powder treated with the adhesive substance was 0.4 mg per 2032 coin-type battery.

[Evaluation of battery performance using lithium-containing separator]
A 2032 type coin battery for evaluation was produced using the same material as in Example 1 except that the separator was produced by the above method, and the performance of the battery was evaluated in the same manner as in Example 1. As a result, the initial efficiency was 87% and the cycle retention was 95%.

[Example 3]
The separator described in Example 1 was used as a separator having lithium powder adhered and fixed to the surface. As the negative electrode, the negative electrode active material (conductive silicon composite powder) prepared in Example 1 was used. To this, 10% polyvinylidene fluoride was added, and N-methylpyrrolidone was further added to form a slurry. After being applied to a copper foil and vacuum-dried at 120 ° C. for 1 hour, the negative electrode was pressure-formed by a roller press. As other materials, evaluation 2032 type coin batteries were produced using the same materials as in Example 1, and the performance of the batteries was evaluated in the same manner as in Example 1. As a result, the initial efficiency was 89% and the cycle retention was 75%.

[Comparative Example 2]
In Example 3, a 2032-type coin battery for evaluation similar to that in Example 3 was prepared, except that a 30 μm thick polyethylene microporous film having no lithium powder on the surface was used as a separator. The battery performance was evaluated in the same manner as described above. As a result, the initial efficiency was 73% and the cycle retention was 71%.

[Example 4]
The separator described in Example 2 was used as a separator having lithium powder adhered and fixed to the surface. A 2032 type coin battery for evaluation was produced using the same material as in Example 1 except that the negative electrode described in Example 3 was used, and the battery performance was evaluated in the same manner as in Example 1. . As a result, the initial efficiency was 87% and the cycle retention was 75%.

Claims (7)

  A separator for a non-aqueous secondary battery having lithium powder on the surface.   The separator for a non-aqueous secondary battery according to claim 1, wherein the lithium powder is a metallic lithium powder having a surface stabilized.   The separator for a non-aqueous secondary battery according to claim 1 or 2, wherein a lithium powder having adhesiveness on the surface is adhesively fixed to the separator.   The separator to which the lithium powder is adhesively fixed is obtained by transferring the tackified lithium powder adhesively fixed to the substrate having releasability to the separator and transferring it to the separator side. The separator for non-aqueous secondary batteries according to claim 3.   The nonaqueous electrolyte secondary battery using the separator of any one of Claims 1 thru | or 4.   A separator according to any one of claims 1 to 4, a negative electrode using a negative electrode active material containing silicon and / or silicon oxide capable of occluding and releasing lithium ions, and occluding and absorbing lithium ions. A non-aqueous electrolyte secondary battery comprising: a positive electrode using a positive electrode active material containing a lithium composite oxide or sulfide that can be released; and a non-aqueous electrolyte containing a lithium salt.   A non-aqueous two-sided lithium powder having a lithium powder on the surface is characterized in that the lithium powder imparted with adhesiveness is adhesively fixed to a substrate having releasability and then brought into contact with a separator to transfer the lithium powder to the separator Manufacturing method of separator for secondary battery.