Separator and battery

Abstract

A separator includes a first layer that has a first principal face and a second principal face, and a second layer that is formed on at least one of the first principal face and the second principal face. The first layer is a microporous membrane including a first polymer resin, and the second layer is a microporous membrane including inorganic particles having an electrically insulating property and a second polymer resin.

The application is claimed as follows: 
     
         1 . A battery comprising:
 a positive electrode;   a negative electrode;   an electrolyte; and   a separator,   wherein the separator includes
 a first resin layer having a first principal face and a second principal face, and 
 a second resin layer provided on at least one of the first principal face and the second principal face; 
   wherein the second resin layer includes inorganic particles,   wherein an average particle diameter D20 of the inorganic particles is larger than an average pore diameter of pores opening onto a surface of the first resin layer,   wherein the average particle diameter D20 of the inorganic particles ranges from 0.13 μm to 2.10 μm.   
     
     
         2 . The battery according to  claim 1 , wherein the average particle diameter D20 of the inorganic particles ranges from 0.13 μm to 0.80 μm. 
     
     
         3 . The battery according to  claim 2 , wherein the average particle diameter D20 of the inorganic particles ranges from 0.13 μm to 0.21 μm. 
     
     
         4 . The battery according to  claim 1 , wherein a volume fraction of the inorganic particles in the second resin layer is equal to or greater than 60 vol % and equal to or lower than 90 vol %. 
     
     
         5 . The battery according to  claim 4 , wherein a volume fraction of the inorganic particles in the second resin layer is equal to or greater than 82 vol % and equal to or lower than 90 vol %. 
     
     
         6 . The battery according to  claim 1 , wherein the inorganic particles includes one or more of alumina, silica, zirconia, and titania. 
     
     
         7 . The battery according to  claim 1 , wherein an average particle diameter D90 of the inorganic particles ranges from 2.00 μm to 5.00 μm. 
     
     
         8 . The battery according to  claim 1 , wherein an average particle diameter D90 of the inorganic particles is equal to or less than ⅓ of a thickness of the first resin layer. 
     
     
         9 . The battery according to  claim 1 , wherein a thickness of the first resin layer is equal to or greater than 10.0 μm and less than 30.0 μm. 
     
     
         10 . The battery according to  claim 1 , wherein the average pore diameter of the pores ranges from 0.03 μm to 0.10 μm. 
     
     
         11 . The battery according to  claim 10 , wherein the average pore diameter of the pores ranges from 0.03 μm to 0.05 μm. 
     
     
         12 . The battery according to  claim 1 , wherein the first resin layer includes one or both of polyethylene and polypropylene. 
     
     
         13 . The battery according to  claim 1 , wherein the second resin layer includes one or more of polyvinylidene fluoride, polyhexafluoropropylene, polysiloxane, polyvinyl alcohol, polyacrylic acid, polymethacrylate, styrene-butadiene rubber, and nitrile butadiene rubber. 
     
     
         14 . The battery according to  claim 1 , wherein the second resin layers are formed on both of the first principal face and the second principal face of the first resin layer. 
     
     
         15 . The battery according to  claim 1 , wherein the second resin layer has a fibrillated mesh-shaped structure with the inorganic particles being separately dispersed. 
     
     
         16 . The battery according to  claim 1 , wherein the second resin layer comprises fibrils having an average diameter of equal to or less than 1 μm. 
     
     
         17 . The battery according to  claim 1 , wherein an area density per unit area of the second resin layer is equal to or greater than 0.2 mg/cm 2  and equal to or less than 1.8 mg/cm 2 . 
     
     
         18 . The battery according to  claim 1 , wherein a difference between air permeability of the separator and air permeability of the first layer is equal to or less than 60 sec/100 ml. 
     
     
         19 . The battery according to  claim 1 , wherein an air-permeability rising rate of air permeability at a time when pressure is applied to the separator for two minutes at 60° C. under 50 kgf/cm 2  with respect to air permeability before the pressure load to the separator is equal to or lower than 35%. 
     
     
         20 . The battery according to  claim 1 , wherein the positive electrode, the negative electrode and the separator are stacked and wound to constitute a wound electrode body, and an outer end of the separator is exposed on the periphery of the wound electrode body. 
     
     
         21 . The battery according to  claim 1 , wherein an open-circuit voltage in a fully-charged state is in the range of 4.2 V to 4.6 V. 
     
     
         22 . An electronic apparatus comprising the battery according to  claim 1 . 
     
     
         23 . A separator comprising:
 a first resin layer having a first principal face and a second principal face, and   a second resin layer provided on at least one of the first principal face and the second principal face;   wherein the second resin layer includes inorganic particles,   wherein an average particle diameter D20 of the inorganic particles is larger than an average pore diameter of pores opening onto a surface of the first resin layer,   wherein the average particle diameter D20 of the inorganic particles ranges from 0.13 μm to 2.10 μm.   
     
     
         24 . The separator according to  claim 23 , wherein the average particle diameter D20 of the inorganic particles ranges from 0.13 μm to 0.80 μm. 
     
     
         25 . The separator according to  claim 24 , wherein the average particle diameter D20 of the inorganic particles ranges from 0.13 μm to 0.21 μm.