Nonaqueous electrolyte secondary battery

Abstract

A secondary battery comprising a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte is provided. The electrode material of which the positive and/or negative electrode is made contains hydrophobic spherical silica particles, which are obtained by introducing R 1 SiO 3/2 units on surfaces of hydrophilic spherical silica particles of SiO 2 units, and further introducing R 2 3 SiO 1/2 units on the surfaces, and have an average particle size of 5-1,000 nm, a particle size distribution D 90 /D 10 of 2-3, and an average circularity of 0.8-1. All components of the battery are made hydrophobic for suppressing absorption of water within the battery and entry of water into the battery.

1 . A nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and a nonaqueous electrolyte, wherein
 the positive and/or negative electrode is made of an electrode material containing hydrophobic spherical silica particles,   said hydrophobic spherical silica particles are introduced R 1 SiO 3/2  units wherein R 1  is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 20 carbon atoms on surfaces of hydrophilic spherical silica particles consisting essentially of SiO 2  units, and further introduced R 2   3 SiO 1/2  units wherein R 2  is independently a substituted or unsubstituted monovalent hydrocarbon group of 1 to 6 carbon atoms on the surfaces having R 1 SiO 3/2  units introduced therein,   said spherical silica particles having an average particle size of 5 nm to 1.00 μm, a particle size distribution D 90 /D 10  of up to 3, and an average circularity of 0.8 to 1.   
     
     
         2 . The secondary battery of  claim 1 , wherein said hydrophobic spherical silica particles are obtained through the steps of (A1) subjecting a tetrafunctional silane compound, a partial hydrolytic condensate thereof or a combination thereof to hydrolysis and condensation to form hydrophilic spherical silica particles consisting essentially of SiO 2  units, (A2) introducing R 1 SiO 3/2  units wherein R 1  is as defined above on surfaces of the hydrophilic spherical silica particles, and (A3) further introducing R 2   3 SiO 1/2  units wherein R 2  is as defined above on the surfaces having R 1 SiO 3/2  units introduced thereon. 
     
     
         3 . The secondary battery of  claim 1 , wherein said hydrophobic spherical silica particles are obtained through the steps of (A1) forming hydrophilic spherical silica particles, (A2) first hydrophobic surface treatment with trifunctional silane compound, and (A3) second hydrophobic surface treatment with monofunctional silane compound, wherein
 the step (A1) of forming hydrophilic spherical silica particles includes subjecting a tetrafunctional silane compound having the general formula (I):
   Si(OR 3 ) 4   (I)
 
   
       wherein R 3  is each independently a monovalent hydrocarbon group of 1 to 6 carbon atoms, a partial hydrolyzate thereof or a mixture thereof to hydrolysis and condensation in a mixture of a hydrophilic organic solvent and water in the presence of a basic substance, thereby forming a dispersion of hydrophilic spherical silica particles consisting essentially of SiO 2  units in the solvent mixture,
 the first hydrophobic surface treatment (A2) includes adding a trifunctional silane compound having the general formula (II):
   R 1 Si(OR 4 ) 3   (II)
 
 
 
       wherein R 1  is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 20 carbon atoms, and R 4  is each independently a monovalent hydrocarbon group of 1 to 6 carbon atoms, a partial hydrolyzate thereof or a mixture thereof to the dispersion from step (A1), for conducting surface treatment of the hydrophilic spherical silica particles, thereby obtaining a dispersion of spherical silica particles having R 1 SiO 3/2  units (wherein R 1  is as defined above) introduced on their surface in the solvent mixture,
 the second hydrophobic surface treatment (A3) includes adding a silazane compound having the general formula (III):
   R 2   3 SiNHSiR 2   3   (III)
 
 
 
       wherein R 2  is each independently a substituted or unsubstituted monovalent hydrocarbon group of 1 to 6 carbon atoms, a monofunctional silane compound having the general formula (IV):
   R 2   3 SiX  (IV)
 
 
       wherein R 2  is as defined above and X is an OH group or hydrolyzable group, or a mixture thereof to the dispersion from step (A2), for conducting surface treatment of the spherical silica particles having R 1 SiO 3/2  units introduced thereon, thereby introducing R 2   3 SiO 1/2  units (wherein R 2  is as defined above) on their surface. 
     
     
         4 . The secondary battery of  claim 1 , wherein
 the positive electrode is made of a positive electrode material containing 0.1 to 5% by weight as solids of the hydrophobic spherical silica particles based on the weight of the positive electrode material.   
     
     
         5 . The secondary battery of  claim 1 , wherein the negative electrode is made of a negative electrode material containing 0.1 to 5% by weight as solids of the hydrophobic spherical silica particles based on the weight of the negative electrode material.