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US-12627004-B2 - Nonaqueous electrolyte secondary battery

US12627004B2US 12627004 B2US12627004 B2US 12627004B2US-12627004-B2

Abstract

In a nonaqueous electrolyte secondary battery which is an example of the embodiment of the present invention, a separator comprises a porous base material, a first filler layer that includes phosphate particles and is formed on one side of the base material, and a second filler layer that includes inorganic particles which have a melting point that is higher than that of the phosphate particles and is formed on the other side of the base material. The volume-based 10% particle size (D 10 ) of the phosphate particles is 0.02 to 0.5 μm and is smaller than the average pore size of the base material. A portion of the phosphate particles penetrates into voids of the base material, and an average value of penetration depth of the particles is 0.1 to 2 μm.

Inventors

  • Masanori SUGIMORI
  • Yasunori Baba
  • Katsunori Yanagida
  • Nobuhiro Hirano

Assignees

  • PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.

Dates

Publication Date
20260512
Application Date
20190225
Priority Date
20180830

Claims (7)

  1. 1 . A non-aqueous electrolyte secondary battery comprising: a positive electrode; a negative electrode; and a separator interposed between the positive electrode and the negative electrode, wherein the separator includes: a porous base material; a first filler layer including phosphate particles and formed on one surface of the base material; and a second filler layer including inorganic particles having a melting point higher than that of the phosphate particles and formed on the other surface of the base material, a volume-based 10% particle size (D 10 ) of the phosphate particles is 0.02 μm or more and 0.15 μm or less, and is smaller than an average pore size of the base material, and some of the phosphate particles enter pores of the base material, and an average value of an entry depth of the particles is 0.1 μm or more and 3 μm or less, wherein the phosphate particles consist essentially of particles of phosphate being at least one selected from the group consisting of LiPON, Li 2 HPO 4 , LiH 2 PO 4 , Na 3 PO 4 , Na 2 HPO 4 , NaH 2 PO 4 , Zr 3 (PO 4 ) 4 , Zr(HPO 4 ) 2 , HZr 2 (PO 4 ) 3 , K 3 PO 4 , K 2 HPO 4 , KH 2 PO 4 , Ca 3 (PO 4 ) 2 , CaHPO 4 , Mg 3 (PO 4 ) 2 , MgHPO 4 , and combinations thereof, the first filler layer consists essentially of the phosphate particles and a first binder, and the second filler layer consists essentially of the inorganic particles, different from the phosphate particles, and a second binder.
  2. 2 . The non-aqueous electrolyte secondary battery according to claim 1 , wherein a volume-based 90% particle size (D 90 ) of the phosphate particles is larger than the average pore size of the base material.
  3. 3 . The non-aqueous electrolyte secondary battery according to claim 1 , wherein the average pore size of the base material is 0.03 μm or more and 1 μm or less.
  4. 4 . The non-aqueous electrolyte secondary battery according to claim 1 , wherein the first filler layer is in contact with a surface of the positive electrode.
  5. 5 . The non-aqueous electrolyte secondary battery according to claim 1 , wherein a BET specific surface area of the phosphate particles is 5 m 2 /g or more and 100 m 2 /g or less.
  6. 6 . The non-aqueous electrolyte secondary battery according to claim 1 , wherein the base material includes a polyolefin as a main component.
  7. 7 . The non-aqueous electrolyte secondary battery according to claim 1 , wherein the average value of an entry depth of the particles is 2 μm or less.

Description

TECHNICAL FIELD The present disclosure relates to a non-aqueous electrolyte secondary battery. BACKGROUND ART A non-aqueous electrolyte secondary battery such as a lithium ion battery may abnormally generate heat due to overcharging, an internal short circuit, an external short circuit, excessive resistance heating caused by a large current, or the like. Conventionally, a separator shutdown function has been known as one of the techniques for suppressing heat generation of a non-aqueous electrolyte secondary battery. The shutdown function is to block the ion conduction (movement of lithium ions) between the positive and negative electrodes by causing the separator to melt because of abnormal heat generation of a battery and closing pores of the separator, to thereby suppress further heat generation of the battery. For example, Patent Literatures 1 and 2 disclose a separator for a non-aqueous electrolyte secondary battery in which a layer including inorganic particles of aluminum oxide or the like is formed on the surface of a porous base material having a shutdown function. CITATION LIST Patent Literature PATENT LITERATURE 1: Japanese Unexamined Patent Application Publication No. 2017-63041PATENT LITERATURE 2: Japanese Patent Publication No. 5774249 SUMMARY As described above, it is an important issue to suppress the heat generation of a battery by blocking the ion conduction between the positive and negative electrodes when the battery abnormally generates heat. However, conventional techniques including the techniques of Patent Literatures 1 and 2 may not be able to sufficiently block the ion conduction between the positive and negative electrodes. In recent years, with the demand for a higher capacity of a battery, thinning of the separator has been studied, but when the thickness of the separator becomes thin, it becomes difficult to exhibit the shutdown function, and meltdown becomes likely to occur. It is an advantage of the present disclosure to sufficiently block the ion conduction between the positive and negative electrodes when an abnormality occurs, to suppress further heat generation of the battery. The non-aqueous electrolyte secondary battery which is one aspect of the present disclosure is a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the separator includes a porous base material, a first filler layer including phosphate particles and formed on one surface of the base material, and a second filler layer including inorganic particles having a melting point higher than that of the phosphate particles and formed on the other surface of the base material. The volume-based 10% particle size (D10) of the phosphate particles is 0.02 μm or more and 0.5 μm or less, and is smaller than the average pore size of the base material, and some of the phosphate particles enter pores of the base material, and the average value of the entry depth of the particles is 0.1 μm or more and 3 μm or less. Advantageous Effect of Invention According to the non-aqueous electrolyte secondary battery, which is one aspect of the present disclosure, it is possible to sufficiently suppress heat generation when an abnormality occurs. For example, it is possible to suppress the shrinkage of the separator when an abnormality occurs in the battery and maintain the shape of the separator that can exhibit the shutdown function. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery, which is an example of an embodiment. FIG. 2 is a cross-sectional view of an electrode assembly, which is an example of an embodiment. DESCRIPTION OF EMBODIMENTS As described above, a separator in which a filler layer including inorganic particles is formed on a porous resin base material is known. In general, the porous resin base material has a shutdown function. Therefore, when the battery abnormally generates heat, the shutdown function of the resin base material blocks the ion conduction between the positive and negative electrodes to suppress further heat generation of the battery. However, as the capacity and energy density of the battery increase, the temperature inside the battery becomes very high (for example, 200° C. or more) when an abnormality occurs, and the shape of the separator may not be able to be secured. Even if the meltdown is not reached, when the separator is greatly deformed by heat, the ion conduction or the like between the positive and negative electrodes cannot be sufficiently blocked, and it becomes difficult to suppress the heat generation of the battery. In view of this situation, as a result of diligent studies by the present inventors, the present inventors have found that by using the above separator having a first filler layer, a second filler layer, and a base material in which some of the phosphate particles include