Secondary battery and method for producing the same
View Patent ↗In a secondary battery including a positive electrode, a negative electrode and a porous film bonded to the surface of at least one of the positive electrode and the negative electrode, the porous film includes ceramic particles and a binder, and the ceramic particles include polycrystalline particles obtained by mechanically crushing a fired material comprising a ceramic that is directly synthesized from a ceramic precursor. The porous film has a porosity of 40 to 80%, for example. The porous film can be formed by a method including the steps of: obtaining a fired material comprising a ceramic from a ceramic precursor; obtaining ceramic particles by mechanically crushing the fired material of the ceramic; obtaining a slurry including the ceramic particles and a binder; and applying the slurry onto the surface of an electrode, followed by drying.
1. A secondary battery comprising: a positive electrode; a negative electrode; and a porous film that is bonded to a surface of at least one electrode selected from said positive electrode and said negative electrode,
wherein said porous film includes ceramic particles and a binder,
said ceramic particles include polycrystalline particles including single crystal cores obtained by mechanically crushing a fired material comprising a ceramic,
a neck is formed between at least a pair of said single crystal cores, said neck comprising the same material as said single crystal cores, and
said polycrystalline particles have a dendritic or coralloid shape.
2. The secondary battery in accordance with claim 1 ,
wherein said polycrystalline particles comprise alumina.
3. The secondary battery in accordance with claim 1 ,
wherein said ceramic particles have a bulk density of 0.1 to 0.8 g/cm 3 .
4. The secondary battery in accordance with claim 1 ,
wherein said ceramic particles have a BET specific surface area of 3 to 20 m 2 /g.
5. The secondary battery in accordance with claim 1 ,
wherein not less than 70 wt % of said ceramic particles is constituted by said polycrystalline particles, and less than 30 wt % thereof is constituted by other particles.
6. The secondary battery in accordance with claim 5 ,
wherein at least a portion of said other particles comprises at least one selected from the group consisting of alumina, magnesia, silica and zirconia.
7. The secondary battery in accordance with claim 1 ,
wherein said porous film has a porosity of 40 to 80%.
8. The secondary battery in accordance with claim 1 ,
further comprising a separator interposed between said positive electrode and said negative electrode.
9. The secondary battery in accordance with claim 1 ,
wherein said single crystal cores have an average particle size of 0.05 μm to 1 μm.
10. The secondary battery in accordance with claim 1 ,
wherein said polycrystalline particles include not less than 3 and not more than 30 single crystal cores, on average.
11. A secondary battery comprising: a positive electrode; a negative electrode; and a porous film that is bonded to a surface of at least one electrode selected from said positive electrode and said negative electrode,
wherein said porous film includes ceramic particles and a binder,
said ceramic particles include polycrystalline particles including single crystal cores obtained by mechanically crushing a fired material comprising a ceramic,
a neck is formed between at least a pair of said single crystal cores, said neck comprising the same material as said single crystal cores, and
said polycrystalline particles have a dendritic or coralloid shape, and said polycrystalline particles having a dendritic or coralloid shape are bound by the binder to form a three-dimensional structure having a three-dimensional void structure therein.
12. A secondary battery comprising: a positive electrode; a negative electrode; and a porous film that is bonded to a surface of at least one electrode selected from said positive electrode and said negative electrode,
wherein said porous film includes ceramic particles and a resin binder, said binder being present in said porous film in a lower amount by weight than said ceramic particles,
said ceramic particles include polycrystalline particles including single crystal cores obtained by mechanically crushing a fired material comprising a ceramic,
a neck is formed between at least a pair of said single cores, said neck comprising the same material as said single crystal cores, and
said polycrystalline particles have a dendritic or coralloid shape.