JP6625147B2 - Secondary battery separator and method of manufacturing the same - Google Patents
Secondary battery separator and method of manufacturing the same Download PDFInfo
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- JP6625147B2 JP6625147B2 JP2018016866A JP2018016866A JP6625147B2 JP 6625147 B2 JP6625147 B2 JP 6625147B2 JP 2018016866 A JP2018016866 A JP 2018016866A JP 2018016866 A JP2018016866 A JP 2018016866A JP 6625147 B2 JP6625147 B2 JP 6625147B2
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- 238000004519 manufacturing process Methods 0.000 title claims description 7
- 239000002002 slurry Substances 0.000 claims description 64
- 239000000919 ceramic Substances 0.000 claims description 49
- 239000004745 nonwoven fabric Substances 0.000 claims description 44
- 229920002678 cellulose Polymers 0.000 claims description 34
- 239000001913 cellulose Substances 0.000 claims description 34
- 239000002121 nanofiber Substances 0.000 claims description 33
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 28
- 239000002105 nanoparticle Substances 0.000 claims description 28
- 229910002706 AlOOH Inorganic materials 0.000 claims description 21
- 239000002245 particle Substances 0.000 claims description 14
- 239000002994 raw material Substances 0.000 claims description 13
- 150000001875 compounds Chemical class 0.000 claims description 11
- 229910052751 metal Inorganic materials 0.000 claims description 11
- 239000002184 metal Substances 0.000 claims description 10
- 239000000835 fiber Substances 0.000 claims description 8
- 238000000465 moulding Methods 0.000 claims description 5
- 238000003491 array Methods 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 28
- 239000010408 film Substances 0.000 description 17
- 229910001593 boehmite Inorganic materials 0.000 description 14
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 14
- 238000010438 heat treatment Methods 0.000 description 13
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- 239000012528 membrane Substances 0.000 description 9
- 238000000034 method Methods 0.000 description 9
- 238000002156 mixing Methods 0.000 description 9
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 8
- 229910004298 SiO 2 Inorganic materials 0.000 description 8
- 238000007602 hot air drying Methods 0.000 description 7
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 6
- 239000007795 chemical reaction product Substances 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 238000001914 filtration Methods 0.000 description 5
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 4
- TYYRFZAVEXQXSN-UHFFFAOYSA-H aluminium sulfate hexadecahydrate Chemical compound O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.[Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O TYYRFZAVEXQXSN-UHFFFAOYSA-H 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 229910010413 TiO 2 Inorganic materials 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 3
- 239000011575 calcium Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000008151 electrolyte solution Substances 0.000 description 3
- 150000004679 hydroxides Chemical class 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 238000006386 neutralization reaction Methods 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 239000007774 positive electrode material Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- RGSFGYAAUTVSQA-UHFFFAOYSA-N Cyclopentane Chemical compound C1CCCC1 RGSFGYAAUTVSQA-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 229910006404 SnO 2 Inorganic materials 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 2
- 210000002421 cell wall Anatomy 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000011267 electrode slurry Substances 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- VASIZKWUTCETSD-UHFFFAOYSA-N manganese(II) oxide Inorganic materials [Mn]=O VASIZKWUTCETSD-UHFFFAOYSA-N 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 150000002736 metal compounds Chemical class 0.000 description 2
- 229910000000 metal hydroxide Inorganic materials 0.000 description 2
- 150000004692 metal hydroxides Chemical class 0.000 description 2
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000011255 nonaqueous electrolyte Substances 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- -1 oxides Chemical class 0.000 description 2
- 229920000098 polyolefin Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- 238000005979 thermal decomposition reaction Methods 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- OERNJTNJEZOPIA-UHFFFAOYSA-N zirconium nitrate Chemical compound [Zr+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O OERNJTNJEZOPIA-UHFFFAOYSA-N 0.000 description 2
- 229910017119 AlPO Inorganic materials 0.000 description 1
- 229920003043 Cellulose fiber Polymers 0.000 description 1
- 229910020599 Co 3 O 4 Inorganic materials 0.000 description 1
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 229910015855 LiMn0.7Fe0.3PO4 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 229910006219 ZrO(NO3)2·2H2O Inorganic materials 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 150000001338 aliphatic hydrocarbons Chemical class 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 150000004945 aromatic hydrocarbons Chemical class 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000001639 boron compounds Chemical class 0.000 description 1
- 229940043430 calcium compound Drugs 0.000 description 1
- 150000001674 calcium compounds Chemical class 0.000 description 1
- 238000007600 charging Methods 0.000 description 1
- 150000001845 chromium compounds Chemical class 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 125000000753 cycloalkyl group Chemical group 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000002612 dispersion medium Substances 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000004108 freeze drying Methods 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 150000008282 halocarbons Chemical class 0.000 description 1
- DMEGYFMYUHOHGS-UHFFFAOYSA-N heptamethylene Natural products C1CCCCCC1 DMEGYFMYUHOHGS-UHFFFAOYSA-N 0.000 description 1
- 230000002209 hydrophobic effect Effects 0.000 description 1
- 238000010335 hydrothermal treatment Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000003273 ketjen black Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 description 1
- 150000002681 magnesium compounds Chemical class 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 150000002816 nickel compounds Chemical class 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 239000005486 organic electrolyte Substances 0.000 description 1
- 150000003891 oxalate salts Chemical class 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920005672 polyolefin resin Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002040 relaxant effect Effects 0.000 description 1
- 150000003377 silicon compounds Chemical class 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Cell Separators (AREA)
Description
本発明は、二次電池用セパレータ及びその製造方法に関する。 The present invention relates to a separator for a secondary battery and a method for manufacturing the same.
高エネルギー密度を有するリチウムイオン二次電池を代表とする二次電池は、携帯型電気機器や電気自転車等の電源として利用が拡大している中、さらなる高容量化や大電流での充放電といった性能が求められている。さらに、二次電池は水系の電解液を用いることができないため、十分な耐酸化還元性を有する非水電解液（有機電解液）を用いているが、それら非水電解液は可燃性であるため発火等の危険性があることから、二次電池には安全性の向上も要求されている。 Secondary batteries, such as lithium ion secondary batteries with high energy densities, are expanding their use as power sources for portable electric devices and electric bicycles. Performance is required. Furthermore, since a secondary battery cannot use an aqueous electrolyte, a nonaqueous electrolyte (organic electrolyte) having sufficient oxidation-reduction resistance is used, but these nonaqueous electrolytes are flammable. For this reason, there is a risk of ignition or the like, so that the secondary battery is also required to have improved safety.
例えば、リチウムイオン二次電池用セパレータとして使用されているポリオレフィン系樹脂の多孔質フィルムは、１２０℃付近の温度で溶融することによって自身の孔を閉塞し、電流やイオンの流れを遮断することによって電池の温度上昇を抑制するシャットダウン機能を有している。しかしながら、外熱等による温度上昇が生じた場合には、シャットダウン機能が働いても電池温度はさらに上昇し、例えば、電池温度が１５０℃以上にまで達した場合には、多孔質フィルムが収縮して正負極を隔離する機能が失われ、内部短絡が生じて発火等を引き起こす。 For example, a porous film of a polyolefin resin used as a separator for lithium ion secondary batteries closes its own pores by melting at a temperature around 120 ° C., and shuts off the flow of current and ions. It has a shutdown function to suppress battery temperature rise. However, when the temperature rises due to external heat or the like, the battery temperature further rises even when the shutdown function operates. For example, when the battery temperature reaches 150 ° C. or more, the porous film shrinks. As a result, the function of isolating the positive electrode and the negative electrode is lost, and an internal short circuit occurs to cause ignition.
このような課題に対し、ｎｍサイズの繊維径を有するセルロース繊維（セルロースナノファイバー）を使用したセパレータが開発されている。しかし、セルロースナノファイバーで形成されたセパレータは、隔離性能などが向上する反面、内部抵抗が大きい。セルロースナノファイバーを用いたセパレータの内部抵抗を緩和させる方法として、下記特許文献１には、繊維径１μｍ以下のセルロースを原料とすることによって得られた、多孔質で低密度であると共に、気密性の高いセパレータが開示されている。 To solve such a problem, a separator using a cellulose fiber (cellulose nanofiber) having a fiber diameter of nm size has been developed. However, separators formed of cellulose nanofibers have high internal resistance, while improving isolation performance and the like. As a method of relaxing the internal resistance of a separator using cellulose nanofibers, Patent Document 1 listed below discloses a porous, low-density and airtight material obtained by using cellulose having a fiber diameter of 1 μm or less as a raw material. Are disclosed.
しかしながら、特許文献１のセパレータは、用いるセルロースナノファイバーが１００ＭＰａを超える高圧でホモジナイズされているため、生産性が著しく低いという課題を有している。 However, the separator of Patent Document 1 has a problem that productivity is extremely low because the cellulose nanofiber used is homogenized at a high pressure exceeding 100 MPa.
本発明は、耐熱性に優れ、内部抵抗が低く、簡易な方法で製造が可能な二次電池用セパレータを提供することを目的とする。 An object of the present invention is to provide a separator for a secondary battery that has excellent heat resistance, low internal resistance, and can be manufactured by a simple method.
本発明者らは、鋭意検討した結果、水熱法を用いて得られる、セルロースナノファイバー（以下、「ＣＮＦ」とも称される。）に複数のｎｍサイズのセラミックス粒子（以下、「セラミックスナノ粒子」と称する。）が直線的に連続して配列してなる形状を呈するｎｍサイズの集合体（以下、「ナノアレイ」と称する。）を、不織布に成型することで、薄膜でありながらも耐熱性に優れた不織布が得られることを見出し、本発明を完成させるに至った。 The present inventors have conducted intensive studies and found that a plurality of nanometer-sized ceramic particles (hereinafter, referred to as “ceramic nanoparticles”) are formed on a cellulose nanofiber (hereinafter, also referred to as “CNF”) obtained by using a hydrothermal method. ) Is formed into a non-woven fabric by forming a nanometer-sized aggregate (hereinafter, referred to as a “nanoarray”) having a shape formed by linearly and continuously arranged, so that it is a thin film and has heat resistance. It has been found that an excellent nonwoven fabric can be obtained, and the present invention has been completed.
本発明によれば、耐熱性に優れると共に、かかる優れた耐熱性により薄膜化が可能となることで内部抵抗が有効に緩和されて充放電特性にも優れる二次電池用セパレータが、簡易な方法で実現される。 Advantageous Effects of Invention According to the present invention, a separator for a secondary battery that is excellent in heat resistance and has excellent charge-discharge characteristics by effectively reducing internal resistance by being able to be thinned by such excellent heat resistance is a simple method. Is realized.
前記ナノアレイは、セラミックスナノ粒子がｎｍサイズの繊維径を有するＣＮＦに担持又は誘導されてなる特異な形状を呈している。そして、このナノアレイは、構成材料の分離が生じ難いため、容易に不織布に成型することができ、これを用いた任意の膜厚を有する二次電池用セパレータを容易に製造することが可能である。 The nanoarray has a unique shape in which ceramic nanoparticles are carried or guided by CNF having a fiber diameter of nm size. This nanoarray can be easily formed into a nonwoven fabric because the constituent materials are unlikely to be separated from each other, and a secondary battery separator having an arbitrary film thickness using the nanoarray can be easily manufactured. .
また、本発明に係る二次電池用セパレータの製造方法は、
次の工程（Ｉ）〜（III）：
（Ｉ）少なくとも１種の金属元素を含むセラミックス原料化合物及びセルロースナノファイバーを含有するスラリーを調製する工程、
（II）前記工程（Ｉ）で得られたスラリーを、水熱反応に付してナノアレイを得る工程、及び
（III）前記工程（II）で得られた前記ナノアレイを不織布に成型する工程
を含むことを特徴とする。
Further, the method for producing a separator for a secondary battery according to the present invention,
The following steps (I) to (III):
(I) a step of preparing a slurry containing a ceramic raw material compound containing at least one metal element and cellulose nanofibers;
(II) a step of subjecting the slurry obtained in the step (I) to a hydrothermal reaction to obtain a nanoarray, and (III) a step of molding the nanoarray obtained in the step (II) into a nonwoven fabric. It is characterized by the following.
かかる方法により、簡易な方法によって耐熱性に優れた不織布を製造することができ、この不織布を二次電池用セパレータとすることで、耐熱性と充放電特性に優れた二次電池が実現される。 By this method, a nonwoven fabric having excellent heat resistance can be produced by a simple method. By using this nonwoven fabric as a separator for a secondary battery, a secondary battery having excellent heat resistance and charge / discharge characteristics is realized. .
本発明によれば、耐熱性及び充放電特性に優れると共に、簡易な方法で製造が可能な二次電池用セパレータが実現される。 ADVANTAGE OF THE INVENTION According to this invention, while being excellent in heat resistance and charge / discharge characteristics, the separator for secondary batteries which can be manufactured by a simple method is implement | achieved.
以下、本発明について詳細に説明する。 Hereinafter, the present invention will be described in detail.
［構造］
本発明の二次電池用セパレータを構成するナノアレイは、セルロースナノファイバーに複数のセラミックスナノ粒子が直線的に連続して担持してなる、特異な形状を呈する。かかるナノアレイでは、隣接するセラミックスナノ粒子同士は必ずしも接触していなくてもよく、例えばセラミックスナノ粒子の粒径以下の間隔を有していても構わない。
[Construction]
The nanoarray constituting the separator for a secondary battery of the present invention has a unique shape in which a plurality of ceramic nanoparticles are linearly and continuously supported on cellulose nanofibers. In such a nanoarray, adjacent ceramic nanoparticles do not necessarily have to be in contact with each other, and may have an interval equal to or less than the particle diameter of the ceramic nanoparticles, for example.
上記ナノアレイは、セラミックスナノ粒子がＣＮＦに直線的に連続して担持してなるため、凝集抑制を目的としてセラミックスナノ粒子に表面修飾を施したり、分散剤を使用する必要がなく、さらに適度な分散状態を保持していることから、簡便に不織布に成型することができる。また、セラミックスナノ粒子は強固にＣＮＦに担持しているため、ナノアレイが分解してセラミックスナノ粒子が単一の独立粒子として振る舞うことはない。 In the nanoarray, since the ceramic nanoparticles are supported linearly and continuously on the CNF, it is not necessary to perform surface modification on the ceramic nanoparticles for the purpose of suppressing aggregation or use of a dispersant, and more appropriate dispersion is achieved. Since the state is maintained, it can be easily formed into a nonwoven fabric. In addition, since the ceramic nanoparticles are firmly supported on CNF, the nanoarray does not decompose and the ceramic nanoparticles do not behave as a single independent particle.
上記ナノアレイは、ＣＮＦの表面がセラミックスの不均質核生成の核生成部位となり、セラミックスナノ粒子が極細のＣＮＦを囲い込むように結晶成長しつつ、同様に結晶成長中の隣接するナノ粒子と接するまで結晶成長を継続することによって、ナノ粒子が不要に凝集することなく、整然と連なりながらＣＮＦに連続して堅固に担持されて、特異な形状が形成されてなるものと考えられる。 In the nanoarray, the surface of the CNF becomes a nucleation site for heterogeneous nucleation of ceramics, and the ceramic nanoparticle grows so as to surround the ultrafine CNF, and also contacts the adjacent nanoparticle during crystal growth. It is thought that by continuing the crystal growth, the nanoparticles are not unnecessarily aggregated, are continuously and firmly supported on the CNF while being connected in an orderly manner, and form a unique shape.
（ＣＮＦ）
上記ナノアレイを構成するセルロースナノファイバー（ＣＮＦ）とは、全ての植物細胞壁の約５割を占める骨格成分であって、かかる細胞壁を構成する植物繊維をナノサイズまで解繊等することにより得ることができる軽量高強度繊維であり、水への良好な分散性も有している。
(CNF)
The cellulose nanofiber (CNF) constituting the nanoarray is a skeletal component occupying about 50% of all plant cell walls, and can be obtained by, for example, defibrating the plant fibers constituting the cell wall to nano size. It is a lightweight, high-strength fiber that has good dispersibility in water.
ＣＮＦの平均繊維径は、例えば５０ｎｍ以下であって、好ましくは２０ｎｍ以下であり、より好ましくは１０ｎｍ以下である。下限値については特に制限はないが、通常１ｎｍ以上である。 The average fiber diameter of CNF is, for example, 50 nm or less, preferably 20 nm or less, and more preferably 10 nm or less. The lower limit is not particularly limited, but is usually 1 nm or more.
ＣＮＦの平均長さは、不織布への加工を効率的に行う観点から、好ましくは１００ｎｍ〜１００μｍであり、より好ましくは１μｍ〜１００μｍであり、さらに好ましくは５μｍ〜１００μｍである。 The average length of CNF is preferably from 100 nm to 100 μm, more preferably from 1 μm to 100 μm, and still more preferably from 5 μm to 100 μm, from the viewpoint of efficiently processing the nonwoven fabric.
上記ＣＮＦを用いた１０質量％濃度のＣＮＦスラリーの２５℃における粘度は、好ましくは３００００ｍＰａ・ｓ〜２０００００ｍＰａ・ｓであり、より好ましくは４００００ｍＰａ・ｓ〜１５００００ｍＰａ・ｓであり、さらに好ましくは４５０００ｍＰａ・ｓ〜１２００００ｍＰａ・ｓである。 The viscosity of the 10% by mass CNF slurry using CNF at 25 ° C. is preferably 30,000 mPa · s to 200,000 mPa · s, more preferably 40,000 mPa · s to 150,000 mPa · s, and still more preferably 45,000 mPa · s. １２０120,000 mPa · s.
（セラミックスナノ粒子）
ナノアレイを構成するセラミックスナノ粒子としては、少なくとも１種の金属元素を含み、かつナノサイズの粒子を形成することが可能であって、電気絶縁性を有しているものであればよく、特に限定されない。かかるセラミックスナノ粒子としては、金属元素の酸化物、水酸化物、炭酸塩、リン酸塩、及びそれらの複合化物等の粒子が挙げられ、なかでも、加熱された際に吸熱反応である脱水反応が生じて電池の温度上昇を抑制する効果を有する水酸化物又は含水酸化物が好ましい。
(Ceramic nanoparticles)
The ceramic nanoparticles constituting the nanoarray are not particularly limited as long as they contain at least one kind of metal element and can form nano-sized particles and have electrical insulation properties. Not done. Examples of such ceramic nanoparticles include particles of metal element oxides, hydroxides, carbonates, phosphates, and composites thereof. Among them, a dehydration reaction which is an endothermic reaction when heated. Hydroxides or hydrated oxides that have the effect of suppressing the temperature rise of the battery due to the occurrence of are preferred.
セラミックスナノ粒子の構成材料として、具体的には、ＳｉＯ２、ＴｉＯ２、ＺｎＯ２、ＳｎＯ２、Ａｌ２Ｏ３、ＭｎＯ、ＭｎＯ２、ＮｉＯ、Ｅｕ２Ｏ３、Ｙ２Ｏ３、Ｎｂ２Ｏ３、Ｎｂ２Ｏ５、ＩｎＯ、ＺｎＯ、Ｆｅ２Ｏ３、Ｆｅ３Ｏ４、Ｃｏ３Ｏ４、ＺｒＯ２、ＣｅＯ２、ＶＯ２、Ｖ２Ｏ５、ＡｌＯＯＨ、Ｙ３Ａｌ５Ｏ１２、ＢａＴｉＯ３、Ｉｎ２Ｏ３−ＳｎＯ２、ＭｇＯ−Ａｌ２Ｏ３−ＳｉＯ２、ＳｉＯ２−Ａｌ２Ｏ３、ＳｉＯ２−ＴｉＯ２、ＳｉＯ２−ＺｒＯ２、ＴｉＯ２−ＺｒＯ２、ＳｉＯ２−Ａｌ２Ｏ３−ＺｒＯ２、ＡｌＯＯＨ（ベーマイト）、Ａｌ（ＯＨ）３、Ｍｇ（ＯＨ）２、Ｃａ（ＯＨ）２、Ｎｉ（ＯＨ）２、Ｍｎ（ＯＨ）２、Ｆｅ（ＯＨ）２、Ｚｎ（ＯＨ）２、Ｈ３ＢＯ３、Ｃｒ２Ｏ３・ｎＨ２Ｏ、ＣａＯ・ＳｉＯ２・ｎＨ２Ｏ、ＣａＯ・Ａｌ２Ｏ３・ｎＨ２Ｏ、ＣａＣＯ３、ＭｇＣＯ３、ＢａＣＯ３、Ｎａ２ＣＯ３、Ｋ２ＣＯ３、ＡｌＰＯ４、Ｃａ３（ＰＯ４）２等が挙げられる。これらの中では、ＡｌＯＯＨ、ＺｒＯ２、Ａｌ（ＯＨ）３、Ｍｇ（ＯＨ）２、Ｃａ（ＯＨ）２、Ｎｉ（ＯＨ）２、Ｈ３ＢＯ３、Ｃｒ２Ｏ３・ｎＨ２Ｏ、ＣａＯ・ＳｉＯ２・ｎＨ２Ｏ、ＣａＯ・Ａｌ２Ｏ３・ｎＨ２Ｏが好ましく、化学的安定性の高いＡｌＯＯＨ、ＺｒＯ２がより好ましい。 As a constituent material of the ceramic nanoparticles, specifically, SiO 2 , TiO 2 , ZnO 2 , SnO 2 , Al 2 O 3 , MnO, MnO 2 , NiO, Eu 2 O 3 , Y 2 O 3 , Nb 2 O 3, Nb 2 O 5, InO , ZnO, Fe 2 O 3, Fe 3 O 4, Co 3 O 4, ZrO 2, CeO 2, VO 2, V 2 O 5, AlOOH, Y 3 Al 5 O 12, BaTiO 3, In 2 O 3 -SnO 2 , MgO-Al 2 O 3 -SiO 2, SiO 2 -Al 2 O 3, SiO 2 -TiO 2, SiO 2 -ZrO 2, TiO 2 -ZrO 2, SiO 2 -Al 2 O 3 -ZrO 2, AlOOH (boehmite), Al (OH) 3, Mg (OH) 2, Ca (OH) 2, Ni (OH) 2, Mn (OH) 2, Fe (OH) 2 , Zn (OH) 2 , H 3 BO 3 , Cr 2 O 3 .nH 2 O, CaO.SiO 2 .nH 2 O, CaO.Al 2 O 3 .nH 2 O, CaCO 3 , MgCO 3 , BaCO 3 , Na 2 CO 3 , K 2 CO 3 , AlPO 4 , Ca 3 (PO 4 ) 2 and the like. Among these, AlOOH, ZrO 2 , Al (OH) 3 , Mg (OH) 2 , Ca (OH) 2 , Ni (OH) 2 , H 3 BO 3 , Cr 2 O 3 .nH 2 O, CaO. SiO 2 .nH 2 O and CaO.Al 2 O 3 .nH 2 O are preferable, and AlOOH and ZrO 2 having high chemical stability are more preferable.
さらに、ＡｌＯＯＨは、非水系二次電池内に存在するフッ酸から正極を保護し、二次電池の耐久性を改善する効果がある、という観点からも好ましい。すなわち、非水系二次電池においては、フッ酸は正極活物質を侵し耐久性を低下させる原因となるが、ＡｌＯＯＨはフッ酸を吸着・共沈させる機能がある。このため、ＡｌＯＯＨを含有するセパレータを使用すれば、電解液中のフッ酸濃度を低いレベルに維持することが可能となり、二次電池の耐久性を改善することが可能となる。 Furthermore, AlOOH is also preferable from the viewpoint that it has an effect of protecting the positive electrode from hydrofluoric acid existing in the non-aqueous secondary battery and improving the durability of the secondary battery. That is, in a non-aqueous secondary battery, hydrofluoric acid corrodes the positive electrode active material and reduces durability, but AlOOH has a function of adsorbing and coprecipitating hydrofluoric acid. Therefore, if a separator containing AlOOH is used, the concentration of hydrofluoric acid in the electrolytic solution can be maintained at a low level, and the durability of the secondary battery can be improved.
ナノアレイを構成するセラミックスナノ粒子は、微結晶粒子からなる。具体的には、かかるセラミックスナノ粒子の平均粒子径は、好ましくは３０ｎｍ以下であり、より好ましくは２０ｎｍ以下である。下限値については特に制限はないが、通常３ｎｍ以上である。ここで、「平均粒子径」とは、電子顕微鏡による観察において、数十個の粒子の粒子径（長軸の長さ）の測定値の平均値を指す。 Ceramic nanoparticles constituting the nanoarray are composed of microcrystalline particles. Specifically, the average particle diameter of such ceramic nanoparticles is preferably 30 nm or less, more preferably 20 nm or less. The lower limit is not particularly limited, but is usually 3 nm or more. Here, the “average particle diameter” refers to an average value of measured values of particle diameters (lengths of major axes) of several tens of particles observed by an electron microscope.
このように、セラミックスナノ粒子は非常に微小な粒子であり、上記の平均繊維径の非常に細いＣＮＦと相俟って、軸径の非常に細いナノアレイを構成することができるため、薄膜の二次電池用セパレータを形成することが可能となる。 As described above, the ceramic nanoparticles are very fine particles, and together with the above-mentioned CNF having a very small average fiber diameter, can form a nanoarray having a very small shaft diameter. A secondary battery separator can be formed.
セラミックスナノ粒子の晶癖（結晶の外形）としては、板状、針状、六面体、柱状等が挙げられる。なかでも、ＣＮＦとの担持が強固である観点から、ＣＮＦの軸長方向に伸延した六面体粒子が好ましい。 Examples of the crystal habit (crystal outline) of the ceramic nanoparticles include a plate shape, a needle shape, a hexahedron, and a column shape. Above all, hexahedral particles extended in the axial direction of CNF are preferable from the viewpoint of firmly supporting CNF.
なお、上記ナノアレイは、粒子径や形状が均一なセラミックスナノ粒子の集合体であることが好ましいが、粒子径や形状が異なるセラミックスナノ粒子の集合体であってもよく、また化学組成が異なる２種以上のセラミックスナノ粒子の集合体であってもよい。 The nanoarray is preferably an aggregate of ceramic nanoparticles having a uniform particle size and shape, but may be an aggregate of ceramic nanoparticles having a different particle size and shape. An aggregate of more than one kind of ceramic nanoparticles may be used.
（二次電池用セパレータ）
本発明の二次電池用セパレータは、２５０℃で１時間加熱した場合の熱収縮率が、１０％以下であるのが好ましい。熱収縮率が１０％を超える場合は、微小短絡で生じる発熱によりセパレータの破膜面積が広がり、大電流が流れるおそれがある。
(Separator for secondary battery)
The separator for a secondary battery of the present invention preferably has a heat shrinkage of 10% or less when heated at 250 ° C. for 1 hour. When the heat shrinkage exceeds 10%, the heat generated by the minute short circuit may increase the area of the separator rupture, and may cause a large current to flow.
二次電池用セパレータの熱収縮率の測定に際しては、所定の大きさで打ち抜いたセパレータについて、加熱処理前後における直径を複数点測定したときの平均値でもって面積を算定した後、加熱前後における面積の変化率によって熱収縮率を算定すればよい。 When measuring the heat shrinkage of the secondary battery separator, for the separator punched in a predetermined size, after calculating the area by the average value when measuring the diameter at a plurality of points before and after the heat treatment, the area before and after heating The heat shrinkage may be calculated from the rate of change of the heat shrinkage.
二次電池用セパレータの膜厚は、内部抵抗を低める観点から、１７５μｍ以下が好ましく、さらに５０μｍ以下が好ましく、特に３０μｍ以下が好ましい。セパレータの膜厚が１７５μｍを超える場合、セパレータの内部抵抗が高くなり、これを適用した二次電池の出力特性が低下するため好ましくない。 The thickness of the secondary battery separator is preferably 175 μm or less, more preferably 50 μm or less, and particularly preferably 30 μm or less, from the viewpoint of reducing the internal resistance. If the thickness of the separator exceeds 175 μm, the internal resistance of the separator increases, and the output characteristics of the secondary battery using the separator are undesirably reduced.
なお、上記二次電池用セパレータを適用する二次電池は、正極、負極、電解液、及びセパレータを必須構成とするものであれば、特に限定されない。 The secondary battery to which the secondary battery separator is applied is not particularly limited as long as the secondary battery has a positive electrode, a negative electrode, an electrolytic solution, and a separator as essential components.
［製造方法］
本発明に係る二次電池用セパレータは、次の、工程（Ｉ）〜（III）：
（Ｉ）少なくとも１種の金属元素を含むセラミックス原料化合物及びセルロースナノファイバーを含有するスラリーを調製する工程、
（II）前記工程（Ｉ）で得られたスラリーを、水熱反応に付してナノアレイを得る工程、及び
（III）前記工程（II）で得られた前記ナノアレイを不織布に成型する工程
を含む製造方法によって、得ることができる。
[Production method]
The separator for a secondary battery according to the present invention comprises the following steps (I) to (III):
(I) a step of preparing a slurry containing a ceramic raw material compound containing at least one metal element and cellulose nanofibers;
(II) a step of subjecting the slurry obtained in the step (I) to a hydrothermal reaction to obtain a nanoarray; and (III) a step of molding the nanoarray obtained in the step (II) into a nonwoven fabric. It can be obtained by a manufacturing method.
この製造方法を用いることで、簡易な方法により、有用な二次電池用セパレータが形成される。 By using this manufacturing method, a useful secondary battery separator is formed by a simple method.
（工程（Ｉ））
工程（Ｉ）は、少なくとも１種の金属元素を含むセラミックス原料化合物及びセルロースナノファイバーを含有するスラリーを調製する工程である。工程（Ｉ）では、先ず、少なくとも１種の金属元素を含むセラミックス原料化合物、水、及びセルロースナノファイバーを混合してスラリーＡを得る。
(Step (I))
Step (I) is a step of preparing a slurry containing a ceramic raw material compound containing at least one metal element and cellulose nanofibers. In the step (I), first, a slurry A is obtained by mixing a ceramic raw material compound containing at least one metal element, water, and cellulose nanofiber.
セラミックス原料化合物としては、具体的には、例えば、アルミニウム化合物、マグネシウム化合物、カルシウム化合物、ニッケル化合物、クロム化合物、ケイ素化合物又はホウ素化合物等の金属化合物が挙げられる。なかでも、上記金属元素の硫酸塩、硝酸塩、炭酸塩、酢酸塩、シュウ酸塩、酸化物、水酸化物、ハロゲン化物等を好適に使用することができる。 Specific examples of ceramic raw material compounds include metal compounds such as aluminum compounds, magnesium compounds, calcium compounds, nickel compounds, chromium compounds, silicon compounds, and boron compounds. Among them, sulfates, nitrates, carbonates, acetates, oxalates, oxides, hydroxides, halides and the like of the above metal elements can be suitably used.
これらセラミックス原料化合物及びセルロースナノファイバーを混合してスラリーＡを調製する際、水を用いる。かかる水の使用量は、各原料の溶解性又は分散性、撹拌の容易性、及び水熱反応の効率等の観点から、セラミックス原料化合物の金属元素１モルに対して１０モル〜３００モルが好ましく、さらに５０モル〜２００モルが好ましい。また、スラリーＡ中におけるセルロースナノファイバーの含有量は、スラリーＡ中の水１００質量部に対し、好ましくは０．１質量部〜２０質量部であり、より好ましくは０．１質量部〜１０質量部である。 Water is used when preparing the slurry A by mixing these ceramic raw material compounds and cellulose nanofibers. From the viewpoint of the solubility or dispersibility of each raw material, the ease of stirring, and the efficiency of the hydrothermal reaction, the amount of water is preferably 10 mol to 300 mol per 1 mol of the metal element of the ceramic raw material compound. And more preferably 50 mol to 200 mol. Further, the content of the cellulose nanofibers in the slurry A is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the water in the slurry A. Department.
また、セラミックス原料化合物とセルロースナノファイバーとの混合比率は、セルロースナノファイバー１００質量部に対して、セラミックス原料化合物が０．１質量部〜１００００質量部であり、より好ましくは１質量部〜１０００質量部であり、特に好ましくは５質量部〜２００質量部である。セルロースナノファイバーに対する、セラミックス原料化合物の混合量が極めて多くなると、次工程（II）における水熱反応においてナノアレイ化されない余剰の金属成分同士が結合し、大径の結晶となってナノアレイ中の夾雑物となる。夾雑物を含むナノアレイから二次電池用セパレータを形成した場合、かかる夾雑物が電気抵抗となって放電特性が低下したり、夾雑物の周囲に孔径の大きな細孔が生じて短絡を生じる可能性がある。 The mixing ratio of the ceramic raw material compound and the cellulose nanofiber is 0.1 parts by mass to 10000 parts by mass, more preferably 1 part by mass to 1000 parts by mass, based on 100 parts by mass of the cellulose nanofiber. And particularly preferably 5 to 200 parts by mass. When the mixing amount of the ceramic raw material compound with respect to the cellulose nanofiber becomes extremely large, excess metal components that are not converted into a nanoarray in the hydrothermal reaction in the next step (II) are combined with each other to form a large-diameter crystal and contaminants in the nanoarray. It becomes. When a separator for a secondary battery is formed from a nanoarray containing impurities, such impurities may cause electrical resistance and decrease the discharge characteristics, or a short circuit may occur due to the formation of large pores around the impurities. There is.
工程（Ｉ）では、次に、上記スラリーＡにアルカリ溶液を添加してスラリーＢとし、中和反応によって、スラリーＢ中に溶解又は分散している金属成分を金属水酸化物にする。アルカリ溶液を添加するには、２５℃におけるスラリーＢのｐＨが１０〜１４に保持するのに充分な量を滴下するのが好ましい。かかるアルカリ溶液としては、例えば、水酸化ナトリウム、水酸化カリウム、炭酸ナトリウム、アンモニア等の水溶液を用いることができ、そのなかでも、水酸化ナトリウム、炭酸ナトリウム又はそれらの混合溶液を用いるのが好ましい。 In the step (I), an alkali solution is added to the slurry A to form a slurry B, and a metal component dissolved or dispersed in the slurry B is converted to a metal hydroxide by a neutralization reaction. In order to add the alkali solution, it is preferable to add dropwise an amount sufficient to maintain the pH of the slurry B at 25 ° C. at 10 to 14. As the alkaline solution, for example, an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia or the like can be used, and among them, it is preferable to use sodium hydroxide, sodium carbonate or a mixed solution thereof.
スラリーＢは、金属水酸化物を良好に生成させる観点から、撹拌して中和反応を進行させるのが好ましい。中和反応中におけるスラリーＢの温度は、５℃以上が好ましく、より好ましくは１０℃〜６０℃である。また、スラリーＢの撹拌時間は、５分〜１２０分が好ましく、３０分〜６０分がより好ましい。 It is preferable that the slurry B is stirred to allow the neutralization reaction to proceed from the viewpoint of favorably generating a metal hydroxide. The temperature of the slurry B during the neutralization reaction is preferably 5 ° C. or higher, more preferably 10 ° C. to 60 ° C. Further, the stirring time of the slurry B is preferably from 5 minutes to 120 minutes, more preferably from 30 minutes to 60 minutes.
（工程（II））
工程（II）は、得られたスラリーＢを、水熱反応に付して、上記ナノアレイを得る工程である。
(Step (II))
Step (II) is a step of subjecting the obtained slurry B to a hydrothermal reaction to obtain the nanoarray.
水熱反応中の温度は、セルロースナノファイバーの熱分解を抑制する観点から、１９０℃以下が好ましく、１００℃〜１９０℃がより好ましく、１３０℃〜１８０℃がさらに好ましく、１４０℃〜１６０℃が特に好ましい。水熱反応は耐圧容器中で行うのが好ましく、１９０℃以下で行う場合、この時の圧力は１．２ＭＰａ以下であるのが好ましく、１００℃〜１９０℃で水和反応を行う場合、０．１ＭＰａ〜１．２ＭＰａであるのが好ましく、１３０℃〜１８０℃では０．３ＭＰａ〜０．９ＭＰａであるのが好ましく、１４０℃〜１６０℃では０．３ＭＰａ〜０．６ＭＰａであるのが好ましい。水熱反応時間は、０．５時間〜２４時間が好ましく、さらに０．５時間〜１５時間が好ましい。水熱反応時間が２４時間を超える場合、ナノアレイを構成するセラミックスナノ粒子が過剰に大径化するおそれがある。 From the viewpoint of suppressing the thermal decomposition of the cellulose nanofiber, the temperature during the hydrothermal reaction is preferably 190 ° C or lower, more preferably 100 ° C to 190 ° C, further preferably 130 ° C to 180 ° C, and 140 ° C to 160 ° C. Particularly preferred. The hydrothermal reaction is preferably performed in a pressure-resistant container. When the reaction is performed at 190 ° C. or lower, the pressure at this time is preferably 1.2 MPa or less. It is preferably from 1 MPa to 1.2 MPa, preferably from 0.3 MPa to 0.9 MPa at 130 ° C. to 180 ° C., and more preferably from 0.3 MPa to 0.6 MPa at 140 ° C. to 160 ° C. The hydrothermal reaction time is preferably 0.5 hours to 24 hours, more preferably 0.5 hours to 15 hours. If the hydrothermal reaction time exceeds 24 hours, the ceramic nanoparticles constituting the nanoarray may have an excessively large diameter.
得られた水熱反応生成物は、セルロースナノファイバーと金属酸化物、又はセルロースナノファイバーと結晶水を有する金属化合物からなるナノアレイである。 The obtained hydrothermal reaction product is a nanoarray composed of cellulose nanofibers and a metal oxide, or a cellulose nanofiber and a metal compound having water of crystallization.
なお、セルロースナノファイバーの分散性を高めることで、高い分散性を有するナノアレイを得る観点から、工程（Ｉ）においてセルロースナノファイバーのスラリーを予め水熱処理した後、工程（II）においてセラミックス原料化合物のスラリーを添加して水熱反応に付すことによって、ナノアレイを得てもよい。 From the viewpoint of obtaining a nanoarray having high dispersibility by increasing the dispersibility of the cellulose nanofibers, the slurry of the cellulose nanofibers is subjected to hydrothermal treatment in advance in the step (I), and then the ceramic raw material compound is added in the step (II). A nanoarray may be obtained by adding a slurry and subjecting it to a hydrothermal reaction.
（工程（III））
工程（III）は、工程（II）によって得られたナノアレイを不織布に成型する工程である。この工程において、生成される不織布の膜厚が調整される。
(Step (III))
Step (III) is a step of molding the nanoarray obtained in step (II) into a nonwoven fabric. In this step, the thickness of the produced nonwoven fabric is adjusted.
具体的には、工程（II）で得られたナノアレイ又はナノアレイを含むスラリーに水を加えて、ナノアレイが高度に分散したスラリーＣを作製した後、スラリーＣを抄紙法や塗布法により製膜する。 Specifically, after adding water to the nanoarray or the slurry containing the nanoarray obtained in the step (II) to prepare a slurry C in which the nanoarray is highly dispersed, the slurry C is formed into a film by a papermaking method or a coating method. .
スラリーＣの水量は、スラリーＣ中のナノアレイ１００質量部に対して、好ましくは２００質量部〜５００００質量部であり、より好ましくは２５０質量部〜４００００質量部でありであり、特に好ましくは３００質量部〜３００００質量部である。水量が２００質量部未満であると、厚膜、且つ膜厚が不均斉な不織布が生成され、この不織布を二次電池のセパレータとして利用した場合には、セパレータの内部抵抗が上昇して二次電池の出力特性が低下してしまう。 The amount of water in the slurry C is preferably 200 parts by mass to 50,000 parts by mass, more preferably 250 parts by mass to 40000 parts by mass, and particularly preferably 300 parts by mass, based on 100 parts by mass of the nanoarray in the slurry C. Parts to 30,000 parts by mass. When the amount of water is less than 200 parts by mass, a thick film and a non-woven fabric having an uneven thickness are generated. When this non-woven fabric is used as a separator of a secondary battery, the internal resistance of the separator increases and the secondary The output characteristics of the battery deteriorate.
工程（II）で得られたナノアレイは、ろ過後、水で洗浄してから、スラリーＣとするのがよい。洗浄に際しては、ナノアレイ１質量部に対し、水を５質量部〜１００質量部用いるのが好ましい。なお、この水洗浄は、成型後の不織布に対して行ってもよい。 The nanoarray obtained in the step (II) is preferably filtered, washed with water, and then used as a slurry C. In washing, it is preferable to use 5 parts by mass to 100 parts by mass of water with respect to 1 part by mass of the nanoarray. This water washing may be performed on the nonwoven fabric after molding.
スラリーＣは、分散媒に有機溶媒を含んでいてもよい。スラリーＣに有機溶媒を含むことで、ナノアレイが分散して形成する網目構造が、乾燥後の不織布にも保持されやすくすることができる。有機溶媒としては、例えば、脂肪族炭化水素、環状炭化水素、芳香族炭化水素、ハロゲン化炭化水素のような低極性疎水性溶媒の１種又は２種以上が好適に使用できる。より具体的には、例えば、シクロヘキサン、シクロペンタン、ｎ−ヘキサン、トルエン、四塩化炭素が好適に使用できる。 The slurry C may include an organic solvent in the dispersion medium. By including the organic solvent in the slurry C, the network structure formed by dispersing the nanoarray can be easily held by the dried nonwoven fabric. As the organic solvent, for example, one or more of low-polarity hydrophobic solvents such as aliphatic hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons can be suitably used. More specifically, for example, cyclohexane, cyclopentane, n-hexane, toluene, and carbon tetrachloride can be suitably used.
また、不織布の厚みの均一性を確保する観点から、スラリーＣ中のナノアレイは高度に分散させるのが好ましい。かかる分散状態の確保には、具体的には、例えば、ミキサー、ポリトロン、自励式超音波粉砕機、超音波発振機、高圧ホモジナイザーを好適に用いることができる。 From the viewpoint of ensuring the uniformity of the thickness of the nonwoven fabric, it is preferable that the nanoarray in the slurry C be highly dispersed. Specifically, for example, a mixer, a polytron, a self-excited ultrasonic pulverizer, an ultrasonic oscillator, and a high-pressure homogenizer can be suitably used to ensure such a dispersed state.
更に、得られた不織布に含まれる水分を除去するために、必要に応じて乾燥処理が施される。乾燥手段は、温風乾燥、凍結乾燥、真空乾燥が用いられ、温風乾燥が好ましい。温風乾燥を行う場合、温風の温度は、セルロースナノファイバーの熱分解を抑制する観点から、５０℃〜２３０℃であればよく、７０℃〜２００℃が好ましい。また、乾燥に要する処理時間は温度に応じて適宜設定される。 Further, in order to remove moisture contained in the obtained nonwoven fabric, a drying treatment is performed as necessary. As the drying means, hot air drying, freeze drying, and vacuum drying are used, and hot air drying is preferable. When performing hot air drying, the temperature of the hot air may be 50 ° C to 230 ° C, and preferably 70 ° C to 200 ° C, from the viewpoint of suppressing the thermal decomposition of the cellulose nanofiber. The processing time required for drying is appropriately set according to the temperature.
以下、本発明について、実施例に基づき具体的に説明するが、本発明はこれら実施例に限定されるものではない。なお、以下の実施例及び比較例に示す各不織布の膜厚は、膜厚計（Ｍｉｔｕｔｏｙｏ社製、ＩＤ−Ｃ１１２ＸＢ）による測定値である。 Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In addition, the film thickness of each nonwoven fabric shown in the following Examples and Comparative Examples is a value measured by a film thickness meter (manufactured by Mitutoyo, ID-C112XB).
［実施例１：ベーマイト（ＡｌＯＯＨ）からなるナノアレイを含む不織布］
硫酸アルミニウムＡｌ２（ＳＯ４）３・１６Ｈ２Ｏ ３．１５ｇ、セルロースナノファイバー３．８９ｇ（ダイセルファインケム社製、ＫＹ１００Ｇ、含水量９０質量％）、及び水５５ｍＬを６０分間混合してスラリーＡ１を作製した。得られたスラリーＡ１に、１０質量％濃度のＮａＯＨ水溶液１２．０ｇを添加し、５分間混合してスラリーＢ１を作製した。
[Example 1: Nonwoven fabric including nanoarray composed of boehmite (AlOOH)]
3.15 g of aluminum sulfate Al 2 (SO 4 ) 3 .16H 2 O, 3.89 g of cellulose nanofibers (KY100G, manufactured by Daicel Finechem Co., Ltd., water content 90% by mass), and 55 mL of water were mixed for 60 minutes to form slurry A1. Produced. To the obtained slurry A1, 12.0 g of a 10 mass% NaOH aqueous solution was added and mixed for 5 minutes to prepare a slurry B1.
スラリーＢ１をオートクレーブに投入し、１４０℃、０．３６ＭＰａで１時間水熱反応を行った。得られた水熱反応生成物を放冷した後、所定量の水を添加し、撹拌混合して２００ｍＬの希釈スラリーＣ１を得た。 The slurry B1 was charged into an autoclave, and a hydrothermal reaction was performed at 140 ° C. and 0.36 MPa for 1 hour. After allowing the obtained hydrothermal reaction product to cool, a predetermined amount of water was added, and the mixture was stirred and mixed to obtain 200 mL of a diluted slurry C1.
得られた希釈スラリーＣ１のうちの、２０ｍＬの希釈スラリーＣ１をφ５．５ｃｍのろ紙でろ過して、水で洗浄し、ろ過成型膜を得た。成型膜に含まれる水分を除去するために、８０℃、４時間の温風乾燥を行い、ベーマイト（ＡｌＯＯＨ）のセラミックスナノアレイからなる不織布Ｄ１（膜厚３１μｍ、ＢＥＴ比表面積１８８ｍ２／ｇ）を得た。不織布Ｄ１のＳＥＭ観察像を図１に、ＴＥＭ観察像を図２に示す。 Out of the obtained diluted slurry C1, 20 mL of the diluted slurry C1 was filtered with a filter paper having a diameter of 5.5 cm, and washed with water to obtain a filtration molded membrane. In order to remove the moisture contained in the molded film, a hot air drying was performed at 80 ° C. for 4 hours, and a nonwoven fabric D1 (thickness 31 μm, BET specific surface area 188 m 2 / g) composed of a ceramic nanoarray of boehmite (AlOOH) was obtained. Obtained. FIG. 1 shows an SEM observation image of the nonwoven fabric D1, and FIG. 2 shows a TEM observation image.
［実施例２：ＺｒＯ２からなるナノアレイを含む不織布］
硝酸ジルコニウムＺｒＯ（ＮＯ３）２・２Ｈ２Ｏ １．３４ｇ、セルロースナノファイバー３．８９ｇ（ダイセルファインケム社製、ＫＹ１００Ｇ、含水量９０質量％）、及び水５５ｍＬを６０分間混合してスラリーＡ２を作製した。得られたスラリーＡ２に、１０質量％濃度のＮａＯＨ水溶液１２．０ｇを添加し、５分間混合してスラリーＢ２を作製した。
[Example 2: Non-woven fabric including nanoarray composed of ZrO 2 ]
Preparation of zirconium nitrate ZrO (NO 3) 2 · 2H 2 O 1.34g, cellulose nanofibers 3.89 g (Daicel FineChem Co., KY100G, water content 90 wt%), and water 55mL were mixed for 60 minutes a slurry A2 did. To the obtained slurry A2, 12.0 g of a 10% by mass aqueous NaOH solution was added and mixed for 5 minutes to prepare a slurry B2.
スラリーＢ２をオートクレーブに投入し、１４０℃、０．３６ＭＰａで１時間水熱反応を行った。得られた水熱反応生成物を放冷した後、所定量の水を添加し、撹拌混合して２００ｍＬの希釈スラリーＣ２を得た。 The slurry B2 was put into an autoclave, and a hydrothermal reaction was performed at 140 ° C. and 0.36 MPa for 1 hour. After allowing the obtained hydrothermal reaction product to cool, a predetermined amount of water was added, and the mixture was stirred and mixed to obtain 200 mL of a diluted slurry C2.
得られた希釈スラリーＣ２のうちの、２０ｍＬの希釈スラリーＣ２をφ５．５ｃｍのろ紙でろ過して、水で洗浄し、ろ過成型膜を得た。成型膜に含まれる水分を除去するために、８０℃、４時間の温風乾燥を行い、ＺｒＯ２のセラミックスナノアレイからなる不織布Ｄ２（膜厚２７μｍ、ＢＥＴ比表面積２０１ｍ２／ｇ）を得た。 Of the obtained diluted slurry C2, 20 mL of the diluted slurry C2 was filtered with a filter paper having a diameter of 5.5 cm, and washed with water to obtain a filtration molded membrane. In order to remove moisture contained in the molded film, drying with hot air at 80 ° C. for 4 hours was performed to obtain a nonwoven fabric D2 (thickness: 27 μm, BET specific surface area: 201 m 2 / g) composed of a ceramic nanoarray of ZrO 2 . .
［実施例３］
スラリーＡ１に代えて、硫酸アルミニウムＡｌ２（ＳＯ４）３・１６Ｈ２Ｏ ６．３０ｇ、セルロースナノファイバー３．８９ｇ、及び水５５ｍＬを６０分間混合して作製したスラリーＡ３を用いた以外、実施例１と同様の操作を行い、ベーマイト（ＡｌＯＯＨ）のセラミックスナノアレイからなる不織布Ｄ３（膜厚３０μｍ、ＢＥＴ比表面積９３ｍ２／ｇ）を得た。
[Example 3]
Example 2 was repeated except that the slurry A1 was prepared by mixing 6.30 g of aluminum sulfate Al 2 (SO 4 ) 3 .16H 2 O, 3.89 g of cellulose nanofiber, and 55 mL of water for 60 minutes instead of the slurry A1. The same operation as in Example 1 was performed to obtain a nonwoven fabric D3 (thickness: 30 μm, BET specific surface area: 93 m 2 / g) composed of a ceramic nanoarray of boehmite (AlOOH).
［実施例４］
スラリーＡ１に代えて、硫酸アルミニウムＡｌ２（ＳＯ４）３・１６Ｈ２Ｏ ０．０８ｇ、セルロースナノファイバー３．８９ｇ、及び水５５ｍＬを６０分間混合して作製したスラリーＡ４を用いた以外、実施例１と同様の操作を行い、ベーマイト（ＡｌＯＯＨ）のセラミックスナノアレイからなる不織布Ｄ４（膜厚２８μｍ、ＢＥＴ比表面積２６２ｍ２／ｇ）を得た。
[Example 4]
Example 2 was repeated except that the slurry A4 was prepared by mixing 0.08 g of aluminum sulfate Al 2 (SO 4 ) 3 .16H 2 O, 3.89 g of cellulose nanofiber, and 55 mL of water for 60 minutes instead of the slurry A1. By performing the same operation as in Example 1, a nonwoven fabric D4 (film thickness 28 μm, BET specific surface area 262 m 2 / g) composed of a ceramic nanoarray of boehmite (AlOOH) was obtained.
［実施例５］
スラリーＢ１をオートクレーブに投入し、１００℃、０．１０ＭＰａで１時間水熱反応を行った以外は、実施例１と同様の操作を行い、ベーマイト（ＡｌＯＯＨ）のセラミックスナノアレイからなる不織布Ｄ５（膜厚２８μｍ、ＢＥＴ比表面積２０４ｍ２／ｇ）を得た。
[Example 5]
The same operation as in Example 1 was performed except that the slurry B1 was put into an autoclave and a hydrothermal reaction was performed at 100 ° C. and 0.10 MPa for 1 hour, and a nonwoven fabric D5 (membrane) made of a ceramic nanoarray of boehmite (AlOOH) was used. A thickness of 28 μm and a BET specific surface area of 204 m 2 / g) were obtained.
［実施例６］
スラリーＢ１をオートクレーブに投入し、１６０℃、０．６１ＭＰａで１時間水熱反応を行った以外は、実施例１と同様の操作を行い、ベーマイト（ＡｌＯＯＨ）のセラミックスナノアレイからなる不織布Ｄ６（膜厚２８μｍ、ＢＥＴ比表面積９８ｍ２／ｇ）を得た。
[Example 6]
The same operation as in Example 1 was performed except that the slurry B1 was put into an autoclave and a hydrothermal reaction was performed at 160 ° C. and 0.61 MPa for 1 hour, and a nonwoven fabric D6 (membrane) made of a ceramic nanoarray of boehmite (AlOOH) was used. A thickness of 28 μm and a BET specific surface area of 98 m 2 / g) were obtained.
［実施例７］
スラリーＢ１をオートクレーブに投入し、１４０℃、０．３５ＭＰａで２４時間水熱反応を行った以外は、実施例１と同様の操作を行い、ベーマイト（ＡｌＯＯＨ）のセラミックスナノアレイからなる不織布Ｄ７（膜厚３２μｍ、ＢＥＴ比表面積９１ｍ２／ｇ）を得た。
[Example 7]
The same operation as in Example 1 was performed except that the slurry B1 was charged into an autoclave and a hydrothermal reaction was performed at 140 ° C. and 0.35 MPa for 24 hours, and a nonwoven fabric D7 (membrane) made of a ceramic nanoarray of boehmite (AlOOH) was used. A thickness of 32 μm and a BET specific surface area of 91 m 2 / g) were obtained.
［実施例８］
スラリーＢ１をオートクレーブに投入し、１４０℃、０．３５ＭＰａで１時間水熱反応を行った。得られた水熱反応生成物を放冷した後、所定量の水を添加し、撹拌混合して５００ｍＬの希釈スラリーＣ８を得た。得られた希釈スラリーＣ８のうちの、２０ｍＬの希釈スラリーＣ８をφ１８．５ｃｍのろ紙でろ過して、水で洗浄し、ろ過成型膜を得た。成型膜に含まれる水分を除去するために、８０℃、４時間の温風乾燥を行い、ベーマイト（ＡｌＯＯＨ）のセラミックスナノアレイからなる不織布Ｄ８（膜厚７μｍ、ＢＥＴ比表面積１９０ｍ２／ｇ）を得た。
Example 8
The slurry B1 was charged into an autoclave, and a hydrothermal reaction was performed at 140 ° C. and 0.35 MPa for 1 hour. After allowing the obtained hydrothermal reaction product to cool, a predetermined amount of water was added thereto, followed by stirring and mixing to obtain 500 mL of a diluted slurry C8. Out of the obtained diluted slurry C8, 20 mL of the diluted slurry C8 was filtered with a filter paper having a diameter of 18.5 cm, and washed with water to obtain a filtration molded membrane. In order to remove the moisture contained in the molded film, a hot air drying was performed at 80 ° C. for 4 hours, and a nonwoven fabric D8 (thickness: 7 μm, BET specific surface area: 190 m 2 / g) composed of a ceramic nanoarray of boehmite (AlOOH) was obtained. Obtained.
［実施例９］
スラリーＢ１をオートクレーブに投入し、１４０℃、０．３６ＭＰａで１時間水熱反応を行った。得られた水熱反応生成物を放冷した後、所定量の水を添加し、撹拌混合して１００ｍＬの希釈スラリーＣ９を得た。得られた希釈スラリーＣ９のうちの、２０ｍＬの希釈スラリーＣ９をφ５．５ｃｍのろ紙でろ過して、水で洗浄し、ろ過成型膜を得た。成型膜に含まれる水分を除去するために、８０℃、４時間の温風乾燥を行い、ベーマイト（ＡｌＯＯＨ）のセラミックスナノアレイからなる不織布Ｄ９（膜厚４７μｍ、ＢＥＴ比表面積１８７ｍ２／ｇ）を得た。
[Example 9]
The slurry B1 was charged into an autoclave, and a hydrothermal reaction was performed at 140 ° C. and 0.36 MPa for 1 hour. After allowing the obtained hydrothermal reaction product to cool, a predetermined amount of water was added, and the mixture was stirred and mixed to obtain 100 mL of a diluted slurry C9. Of the obtained diluted slurry C9, 20 mL of the diluted slurry C9 was filtered through a filter paper having a diameter of 5.5 cm and washed with water to obtain a filtration molded membrane. In order to remove the moisture contained in the molded film, hot air drying was performed at 80 ° C. for 4 hours, and a nonwoven fabric D9 (47 μm in film thickness, 187 m 2 / g in BET specific surface area) composed of a ceramic nanoarray of boehmite (AlOOH) was obtained. Obtained.
［実施例１０］
スラリーＢ１をオートクレーブに投入し、１４０℃、０．３５ＭＰａで１時間水熱反応を行った。得られた水熱反応生成物８０ｍＬを、希釈せずにφ５．５ｃｍのろ紙でろ過して、水で洗浄し、ろ過成型膜を得た。成型膜に含まれる水分を除去するために、８０℃、４時間の温風乾燥を行い、ベーマイト（ＡｌＯＯＨ）のセラミックスナノアレイからなる不織布Ｄ１０（膜厚１５７μｍ、ＢＥＴ比表面積１８８ｍ２／ｇ）を得た。
[Example 10]
The slurry B1 was charged into an autoclave, and a hydrothermal reaction was performed at 140 ° C. and 0.35 MPa for 1 hour. 80 mL of the obtained hydrothermal reaction product was filtered through a filter paper of 5.5 cm without dilution, and washed with water to obtain a filtration molded membrane. In order to remove the moisture contained in the molded film, a hot air drying was performed at 80 ° C. for 4 hours, and a nonwoven fabric D10 (film thickness 157 μm, BET specific surface area 188 m 2 / g) composed of a ceramic nanoarray of boehmite (AlOOH) was obtained. Obtained.
［比較例１：ポリオレフィン系薄膜］
二次電池用セパレータＥ１として、市販のポリエチレンセパレータ（ダブル・スコープ社製、ＣＯＤ−２０−Ｂ）を採用した（膜厚１５μｍ、ＢＥＴ比表面積３０ｍ２／ｇ）。
[Comparative Example 1: Polyolefin-based thin film]
As the secondary battery separator E1, a commercially available polyethylene separator (COD-20-B, manufactured by Double Scope Co., Ltd.) was used (film thickness 15 μm, BET specific surface area 30 m 2 / g).
［比較例２：ナノアレイが担持されていないセルロースナノファイバーを含む不織布］
スラリーＡ１に代えて、硫酸アルミニウムＡｌ２（ＳＯ４）３・１６Ｈ２Ｏを添加せず、セルロースナノファイバー３．８９ｇ、及び水５５ｍＬを６０分間混合してスラリーＡ１１を作製した。その後は、実施例１と同様の操作を行い、セルロースナノファイバーからなる不織布Ｅ２（膜厚２９μｍ、ＢＥＴ比表面積２７３ｍ２／ｇ）を得た。
[Comparative Example 2: Nonwoven fabric containing cellulose nanofibers not carrying a nanoarray]
Instead of Slurry A1, aluminum sulfate Al 2 (SO 4 ) 3 .16H 2 O was not added, and 3.89 g of cellulose nanofiber and 55 mL of water were mixed for 60 minutes to prepare Slurry A11. Thereafter, the same operation as in Example 1 was performed to obtain a nonwoven fabric E2 made of cellulose nanofibers (film thickness 29 μm, BET specific surface area 273 m 2 / g).
［比較例３］
スラリーＢ１をオートクレーブに投入し、２００℃、１．５４ＭＰａで２４時間水熱反応を行った以外は、実施例１と同様の操作を行い、ベーマイト（ＡｌＯＯＨ）のセラミックスナノアレイからなる不織布Ｅ３（膜厚３３μｍ、ＢＥＴ比表面積２２ｍ２／ｇ）を得た。
[Comparative Example 3]
The same operation as in Example 1 was performed except that the slurry B1 was put into an autoclave and a hydrothermal reaction was performed at 200 ° C. and 1.54 MPa for 24 hours, and a nonwoven fabric E3 (membrane) made of a ceramic nanoarray of boehmite (AlOOH) was used. A thickness of 33 μm and a BET specific surface area of 22 m 2 / g) were obtained.
＜熱収縮率の評価＞
各不織布又は二次電池用セパレータ（Ｄ１〜Ｄ１０、Ｅ１〜Ｅ３）について、１６０℃で１時間の加熱処理を行ったときの加熱前後での熱収縮率、及び２５０℃で１時間の加熱処理を行ったときの加熱前後での熱収縮率を算定した。具体的には、φ１７ｍｍに打ち抜いた各不織布又は二次電池用セパレータの、上記加熱処理後の直径をノギスにより１０点計測し、その平均値から加熱処理後の面積を算出した。なお、１６０℃はポリオレフィン系材料の融点近傍の温度に対応し、２５０℃はセルロースナノファイバーに含有される水分が脱水して脆化が開始される温度に対応する。
<Evaluation of heat shrinkage>
About each nonwoven fabric or the separator for secondary batteries (D1 to D10, E1 to E3), the heat shrinkage before and after heating when the heat treatment was performed at 160 ° C. for 1 hour, and the heat treatment at 250 ° C. for 1 hour. The heat shrinkage before and after heating was calculated. Specifically, the diameter of each nonwoven fabric or secondary battery separator punched to φ17 mm after the above heat treatment was measured at 10 points with calipers, and the area after the heat treatment was calculated from the average value. Note that 160 ° C. corresponds to a temperature near the melting point of the polyolefin-based material, and 250 ° C. corresponds to a temperature at which moisture contained in the cellulose nanofiber is dehydrated and embrittlement starts.
その後、加熱温度１６０℃、加熱温度２５０℃のそれぞれに対し、下記式により熱収縮率を算定した。
熱収縮率＝｛（加熱前の不織布又は二次電池用セパレータの面積）−（加熱後の不織布又は二次電池用セパレータの面積）｝／（加熱前の不織布又は二次電池用セパレータの面積）＊１００
Thereafter, the heat shrinkage was calculated by the following equation for each of the heating temperature of 160 ° C. and the heating temperature of 250 ° C.
Heat shrinkage = {(area of nonwoven fabric or separator for secondary battery before heating) − (area of nonwoven fabric or separator for secondary battery after heating)} / (area of nonwoven fabric or separator for secondary battery before heating) * 100
＜二次電池における充放電特性の評価＞
各不織布又は二次電池用セパレータ（Ｄ１〜Ｄ１０、Ｅ１〜Ｅ３）をセパレータとする、リチウムイオン二次電池を作製した。
<Evaluation of charge / discharge characteristics in secondary battery>
Lithium ion secondary batteries were produced using each nonwoven fabric or secondary battery separator (D1 to D10, E1 to E3) as a separator.
正極活物質には、水熱法で製造したオリビン型リン酸マンガン鉄リチウム（ＬｉＭｎ0.7Ｆｅ0.3ＰＯ4）を用いた。この正極活物質、ケッチェンブラック、ポリフッ化ビニリデンを質量比９０：５：５の配合割合で混合し、これにＮ−メチル−２−ピロリドンを加えて充分混練し、正極スラリーを調製した。次いで、塗工機を用いて、正極スラリーを厚さ２０μｍのアルミニウム箔からなる集電体に塗布し、８０℃で１２時間の真空乾燥を行った。その後、φ１４ｍｍの円盤状に打ち抜いてハンドプレスを用いて１６ＭＰａで２分間プレスし、正極とした。 As the positive electrode active material, olivine-type lithium manganese iron phosphate (LiMn 0.7 Fe 0.3 PO 4 ) produced by a hydrothermal method was used. The positive electrode active material, Ketjen Black, and polyvinylidene fluoride were mixed at a mixing ratio of 90: 5: 5 by mass, N-methyl-2-pyrrolidone was added thereto, and the mixture was sufficiently kneaded to prepare a positive electrode slurry. Next, using a coating machine, the positive electrode slurry was applied to a current collector made of an aluminum foil having a thickness of 20 μm, and vacuum-dried at 80 ° C. for 12 hours. Then, it was punched out into a disk shape of φ14 mm and pressed at 16 MPa for 2 minutes using a hand press to obtain a positive electrode.
負極には、φ１５ｍｍに打ち抜いたリチウム箔を用いた。電解液には、エチレンカーボネート及びエチルメチルカーボネートを体積比１：１の割合で混合した混合溶媒に、ＬｉＰＦ6を１ｍｏｌ／Ｌの濃度で溶解したものを用いた。 As the negative electrode, a lithium foil punched into φ15 mm was used. As the electrolytic solution, a solution obtained by dissolving LiPF 6 at a concentration of 1 mol / L in a mixed solvent obtained by mixing ethylene carbonate and ethyl methyl carbonate at a volume ratio of 1: 1 was used.
セパレータには、上記各実施例１〜１０、比較例１〜３で得られた不織布又は二次電池用セパレータ（Ｄ１〜Ｄ１０、Ｅ１〜Ｅ３）を用いた。 As the separator, the nonwoven fabric or the secondary battery separator (D1 to D10, E1 to E3) obtained in each of Examples 1 to 10 and Comparative Examples 1 to 3 was used.
これらの電池部品を露点が−５０℃以下の雰囲気で常法により組み込み収容し、コイン型二次電池（ＣＲ−２０３２）を得た。 These battery parts were incorporated and housed in a conventional manner in an atmosphere having a dew point of -50 ° C or lower, to obtain a coin-type secondary battery (CR-2032).
得られた二次電池を用いて定電流密度での充放電特性を評価した。具体的には、気温３０℃環境において放電容量測定装置（北斗電工社製ＨＪ−１００１ＳＤ８）を用いて行った。このときの充電条件は、電流０．２ＣＡ（１７ｍＡ／ｇ）、電圧４．５Ｖの定電流充電とし、放電条件は、電流０．２ＣＡ又は３ＣＡとし、終止電圧２．０Ｖの定電流放電とした。 The charge / discharge characteristics at a constant current density were evaluated using the obtained secondary battery. Specifically, the measurement was performed in a 30 ° C. environment using a discharge capacity measuring device (HJ-1001SD8 manufactured by Hokuto Denko Corporation). The charging conditions at this time were constant current charging at a current of 0.2 CA (17 mA / g) and a voltage of 4.5 V, and discharging conditions were a constant current discharging at a current of 0.2 CA or 3 CA and a final voltage of 2.0 V. .
得られた結果を表１に示す。 Table 1 shows the obtained results.
表１より、実施例１〜１０により得られた各不織布（Ｄ１〜Ｄ１０）は熱収縮率が小さく、耐熱性に優れることが分かる。また、これらの各不織布（Ｄ１〜Ｄ１０）からなるセパレータを含む二次電池は、上記の優れた耐熱性を有しつつ薄膜化が可能であり、内部抵抗を有効に低下させて充放電特性に優れていることが分かる。 Table 1 shows that each of the nonwoven fabrics (D1 to D10) obtained in Examples 1 to 10 has a small heat shrinkage and is excellent in heat resistance. In addition, a secondary battery including a separator composed of each of these nonwoven fabrics (D1 to D10) can be thinned while having the above-described excellent heat resistance, and effectively reduces internal resistance to improve charge / discharge characteristics. It turns out that it is excellent.
Claims (5)
（Ｉ）少なくとも１種の金属元素を含むセラミックス原料化合物及びセルロースナノファイバーを含有するスラリーを調製する工程、
（II）前記工程（Ｉ）で得られたスラリーを、１００℃以上１９０℃以下で水熱反応に付してナノアレイを得る工程、及び
（III）前記工程（II）で得られた前記ナノアレイを不織布に成型する工程
を含むことを特徴とする、二次電池用セパレータの製造方法。 The following steps (I) to (III):
(I) a step of preparing a slurry containing a ceramic raw material compound containing at least one metal element and cellulose nanofibers;
(II) a step of subjecting the slurry obtained in the step (I) to a hydrothermal reaction at 100 ° C. or more and 190 ° C. or less to obtain a nanoarray; and (III) preparing the nanoarray obtained in the step (II). A method for producing a separator for a secondary battery, comprising a step of molding into a nonwoven fabric.
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