Electrode for lithium-ion secondary battery and manufacturing method thereof, and lithium-ion secondary battery

Abstract

A highly reliable electrode for a lithium-ion secondary battery is provided. A highly reliable lithium-ion secondary battery is also provided using the electrode for a lithium-ion secondary battery. The electrode for a lithium-ion secondary battery includes a current collector and an active material layer. The active material layer includes an active material, graphene, and polyimide. The active material includes a plurality of nanowires each of which grows with a silicon particle used as a nucleus and extends in one direction into a fine needle. The graphene includes a region in contact with the plurality of nanowires, and polyimide includes a region in contact with the graphene. The lithium-ion secondary battery uses the electrode as a negative electrode.

What is claimed is: 
     
         1 . An electrode for a power storage device, comprising:
 a current collector; and   an active material layer over the current collector, the active material layer including an active material, graphene, and a polyimide,   wherein the active material includes a nanowire which extends from a silicon particle.   
     
     
         2 . The electrode for a power storage device, according to  claim 1 ,
 wherein the graphene is in contact with the nanowire, and   wherein the polyimide is in contact with the graphene.   
     
     
         3 . The electrode for a power storage device, according to  claim 1 ,
 wherein the current collector includes stainless steel, iron, copper, titanium, or nickel.   
     
     
         4 . The electrode for a power storage device, according to  claim 1 , further comprising a layer between the current collector and the active material layer. 
     
     
         5 . The electrode for a power storage device, according to  claim 1 ,
 wherein a plurality of nanowires comprises a network of nanowires and at least one of the nanowires extends from the silicon particle.   
     
     
         6 . The electrode for a power storage device, according to  claim 1 ,
 wherein the active material is covered with graphene.   
     
     
         7 . A power storage device comprising:
 a positive electrode including a positive electrode current collector and a positive electrode active material layer; and   a negative electrode including a negative electrode current collector and a negative electrode active material layer,   wherein the negative electrode active material layer includes a negative electrode active material, a first graphene, and a polyimide,   wherein the negative electrode active material includes a nanowire which extends from a silicon particle, and   wherein the positive electrode active material layer includes a positive electrode active material, a second graphene, and polyvinylidene fluoride.   
     
     
         8 . The power storage device according to  claim 7 ,
 wherein the first graphene is in contact with the plurality of nanowires,   wherein the polyimide is in contact with the first graphene,   
     
     
         9 . The power storage device according to  claim 7 ,
 wherein the second graphene is in contact with the positive electrode active material   
     
     
         10 . The power storage device according to  claim 7 ,
 wherein the negative electrode current collector includes stainless steel, iron, copper, titanium, or nickel.   
     
     
         11 . The power storage device according to  claim 7 , further comprising a layer between the negative electrode current collector and the negative electrode active material layer. 
     
     
         12 . The power storage device according to  claim 7 ,
 wherein a plurality of nanowires comprises a network of nanowires and at least one of the nanowires extends from the silicon particle.   
     
     
         13 . The power storage device according to  claim 7 ,
 wherein the negative electrode active material is covered with graphene.   
     
     
         14 . A method for manufacturing an electrode for power storage device, comprising the steps of:
 mixing silicon particles and graphene oxide;   mixing the mixture of the silicon particles and the graphene oxide with a solution of a polyimide precursor and a solvent, thereby obtaining slurry; and   applying a mixture of the silicon particles, the graphene oxide and the polyimide precursor in a solvent; and   heating the applied mixture,   whereby forming a nanowire that grows with a silicon particle used as a nucleus and extends into a fine needle, reducing graphene oxide to graphene, and imidizing the polyimide precursor to be polyimide.   
     
     
         15 . The method for manufacturing an electrode for a power storage device, according to  claim 14 ,
 wherein the mixed solution of the polyimide precursor and the polar solvent has a pH of 2 to 4.