Porous layer
As a nonaqueous electrolyte secondary battery porous layer having an excellent cycle characteristic, provided is a nonaqueous electrolyte secondary battery porous layer containing: an inorganic filler; and a polyvinylidene fluoride-based resin, the nonaqueous electrolyte secondary battery porous layer containing the inorganic filler in an amount of not less than 50% by weight relative to a total weight of the inorganic filler and the polyvinylidene fluoride-based resin, the polyvinylidene fluoride-based resin containing an α-form polyvinylidene fluoride-based resin and a β-form polyvinylidene fluoride-based resin, assuming that a sum of (i) an amount of the α-form polyvinylidene fluoride-based resin and (ii) an amount of the β-form polyvinylidene fluoride-based resin is 100 mol %, the amount of the α-form polyvinylidene fluoride-based resin being not less than 45 mol %.
1. A nonaqueous electrolyte secondary battery porous layer comprising:
an inorganic filler; and
a polyvinylidene fluoride-based resin,
the nonaqueous electrolyte secondary battery porous layer containing the inorganic filler in an amount of not less than 50% by weight relative to a total weight of the inorganic filler and the polyvinylidene fluoride-based resin,
the polyvinylidene fluoride-based resin containing an α-form polyvinylidene fluoride-based resin and a β-form polyvinylidene fluoride-based resin,
assuming that a sum of (i) an amount of the α-form polyvinylidene fluoride-based resin contained in the polyvinylidene fluoride-based resin and (ii) an amount of the β-form polyvinylidene fluoride-based resin contained in the polyvinylidene fluoride-based resin is 100 mol %, the amount of the α-form polyvinylidene fluoride-based resin being not less than 70 mol %,
the amount of the α-form polyvinylidene fluoride-based resin being calculated by (a) waveform separation of (α/2) observed at around −76 ppm in a 19 F-NMR spectrum obtained from the nonaqueous electrolyte secondary battery porous layer and (b) waveform separation of {(α/2)+β} observed at around −95 ppm in the 19 F-NMR spectrum obtained from the nonaqueous electrolyte secondary battery porous layer.
2. The nonaqueous electrolyte secondary battery porous layer as set forth in claim 1 , wherein, assuming that the sum of (i) the amount of the α-form polyvinylidene fluoride-based resin contained in the polyvinylidene fluoride-based resin and (ii) the amount of the (β-form polyvinylidene fluoride-based resin contained in the polyvinylidene fluoride-based resin is 100 mol %, the amount of the α-form polyvinylidene fluoride-based resin is not less than 70 mol % and not more than 83 mol %.
3. The nonaqueous electrolyte secondary battery porous layer as set forth in claim 1 , wherein the nonaqueous electrolyte secondary battery porous layer contains the inorganic filler in an amount of not less than 70% by weight and not more than 99% by weight relative to the total weight of the inorganic filler and the polyvinylidene fluoride-based resin.
4. The nonaqueous electrolyte secondary battery porous layer as set forth in claim 1 , wherein the polyvinylidene fluoride-based resin is polyvinylidene fluoride, a polyvinylidene fluoride copolymer, or a mixture of the polyvinylidene fluoride and the polyvinylidene fluoride copolymer.
5. The nonaqueous electrolyte secondary battery porous layer as set forth in claim 1 , wherein the polyvinylidene fluoride-based resin has a weight-average molecular weight of not less than 300,000 and not more than 3,000,000.
6. The nonaqueous electrolyte secondary battery porous layer as set forth in claim 1 , wherein:
the inorganic filler contains silicon (Si) and/or a silicon compound; and
the inorganic filler contains the silicon (Si) in an amount of not more than 2,000 ppm relative to a total weight of the inorganic filler.
7. A laminated body comprising:
a porous base material containing a polyolefin-based resin in an amount of not less than 50% by volume; anda nonaqueous electrolyte secondary battery porous layer recited in claim 1 ,
the nonaqueous electrolyte secondary battery porous layer being laminated on at least one surface of the porous base material.
8. A nonaqueous electrolyte secondary battery separator comprising:
a porous base material containing a polyolefin-based resin in an amount of not less than 50% by volume; and
a nonaqueous electrolyte secondary battery porous layer recited in claim 1 ,
the nonaqueous electrolyte secondary battery porous layer being laminated on at least one surface of the porous base material.
9. A nonaqueous electrolyte secondary battery electrode comprising:
one of a cathode sheet and an anode sheet; and
a nonaqueous electrolyte secondary battery porous layer recited in claim 1 ,
the nonaqueous electrolyte secondary battery porous layer being laminated on at least one surface of the one of the cathode sheet and the anode sheet.
10. A nonaqueous electrolyte secondary battery member comprising:
a cathode;
a nonaqueous electrolyte secondary battery porous layer recited in claim 1 ; and
an anode,
the cathode, the nonaqueous electrolyte secondary battery porous layer, and the anode being provided in this order.
11. A nonaqueous electrolyte secondary battery comprising:
a nonaqueous electrolyte secondary battery porous layer recited in claim 1 .