Negative electrode for nonaqueous secondary battery, process of producing the negative electrode, and nonaqueous secondary battery

Abstract

Disclosed is a negative electrode for a nonaqueous secondary battery comprised of a current collector and an active material structure containing an electro-conductive material having low capability of forming a lithium compound on at least one side of the current collector, the active material structure containing 5 to 80% by weight of active material particles containing a material having high capability of forming a lithium compound. The active material structure preferably has an active material layer containing the active material particles and a surface coating layer formed on the active material layer.

1 . A negative electrode for a nonaqueous secondary battery comprising a current collector and an active material structure containing an electro-conductive material having low capability of forming a lithium compound on at least one side of the current collector, the active material structure containing 5 to 80% by weight of active material particles containing a material having high capability of forming a lithium compound.  
     
     
         2 . The negative electrode for a nonaqueous secondary battery according to  claim 1 , wherein the active material structure has an active material layer containing the active material particles and a surface coating layer located on the active material layer.  
     
     
         3 . The negative electrode for a nonaqueous secondary battery according to  claim 1 , wherein the material having high capability of forming a lithium compound is tin or silicon.  
     
     
         4 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the active material layer contains 0.1 to 20% by weight of an electro-conductive carbon material.  
     
     
         5 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the material constituting the surface coating layer enters the active material layer or reaches the current collector.  
     
     
         6 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the material constituting the surface coating layer penetrates throughout the active material layer.  
     
     
         7 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the surface coating layer has a large number of micropores extending in the thickness direction of the surface coating layer and allowing a nonaqueous electrolyte to pass therethrough.  
     
     
         8 . The negative electrode for a nonaqueous secondary battery according to  claim 3 , wherein the active material particles are particles of single silicon or single tin.  
     
     
         9 . The negative electrode for a nonaqueous secondary battery according to  claim 3 , wherein the active material particles are mixed particles comprising at least silicon or tin and carbon, the mixed particles containing 10 to 90% by weight of silicon or tin and 10 to 90% by weight of carbon.  
     
     
         10 . The negative electrode for a nonaqueous secondary battery according to  claim 3 , wherein the active material particles are mixed particles comprising silicon or tin and a metal, the mixed particles containing 30% to 99.9% by weight of silicon or tin and 0.1 to 70% by weight of at least one element selected from the group consisting of Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except for a case where the active material particles contain tin), Si (except for a case where the active material particles contain silicon), In, V, Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd, and Nd.  
     
     
         11 . The negative electrode for a nonaqueous secondary battery according to  claim 3 , wherein the active material particles are silicon compound particles or tin compound particles, the silicon compound particles or the tin compound particles containing 30% to 99.9% by weight of silicon or tin and 0.1 to 70% by weight of at least one element selected from the group consisting of Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except for a case where the active material particles contain tin), Si (except for a case where the active material particles contain silicon), In, V, Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd, and Nd.  
     
     
         12 . The negative electrode for a nonaqueous secondary battery according to  claim 3 , wherein the active material particles are mixed particles comprising silicon compound particles or tin compound particles and metal particles, 
 the mixed particles containing 30% to 99.9% by weight of silicon compound particles or tin compound particles and 0.1 to 70% by weight of particles of at least one element selected from the group consisting of Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except for a case where the active material particles contain tin), Si (except for a case where the active material particles contain silicon), In, V, Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd, and Nd, and    the compound particles containing 30% to 99.9% by weight of silicon or tin and 0.1 to 70% by weight of at least one element selected from the group consisting of Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except for a case where the active material particles contain tin), Si (except for a case where the active material particles contain silicon), In, V, Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd, and Nd.    
     
     
         13 . The negative electrode for a nonaqueous secondary battery according to  claim 3 , wherein the active material particles are single silicon or single tin particles coated with a metal, the metal being at least one element selected from the group consisting of Cu, Ag, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except for a case where the active material particles contain tin), Si (except for a case where the active material particles contain silicon), In, V, Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd, and Nd, and the active material particles containing 30% to 99.9% by weight of silicon or tin and 0.1 to 70% by weight of the metal.  
     
     
         14 . The negative electrode for a nonaqueous secondary battery according to  claim 1 , wherein the active material particles have a maximum particle size of 50 μm or smaller.  
     
     
         15 . The negative electrode for a nonaqueous secondary battery according to  claim 1 , wherein the active material particles contain silicon and have an average particle size of 0.1 to 10 μm in terms of D 50  and an oxygen concentration of less than 2.5% by weight, the outermost surface of the active material particles having a silicon concentration of higher than half of an oxygen concentration of the outermost surface.  
     
     
         16 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the surface coating layer contains at least one element selected from the group consisting of Cu, Ag, Ni, Co, Cr, Fe, and In.  
     
     
         17 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the surface coating layer is formed by electroplating.  
     
     
         18 . The negative electrode for a nonaqueous secondary battery according to claim  2 , wherein the surface coating layer is formed by sputtering, chemical vapor deposition or physical vapor deposition.  
     
     
         19 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the surface coating layer is formed by rolling an electro-conductive foil.  
     
     
         20 . The negative electrode for a nonaqueous secondary battery according to  claim 19 , wherein the electro-conductive foil is a metal foil or an electro-conductive plastic foil.  
     
     
         21 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the active material layer is formed by applying a slurry containing the active material particles to a surface of the current collector.  
     
     
         22 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the surface coating layer has a thickness of 0.3 to 50 μm, and the active material layer has a thickness of 1 to 100 μm.  
     
     
         23 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the surface coating layer has a thickness of 0.3 to 50 μm, and the active material structure has a thickness of 2 to 100.  
     
     
         24 . The negative electrode for a nonaqueous secondary battery according to  claim 2 , wherein the surface coating layer has a thickness of 0.3 to 50 μm, and the electrode has a total thickness of 2 to 200 μm.  
     
     
         25 . The negative electrode for a nonaqueous secondary battery according to  claim 1 , wherein the current collector has a large number of micropores of 0.01 to 200 μm in diameter at a density of 5 to 10000 pores per cm 2  and has a thickness of 1 to 100 μm.  
     
     
         26 . The negative electrode for a nonaqueous secondary battery according to  claim 1 , wherein the current collector is formed of punching metal or expanded metal, each having a large number of openings each having an opening area of 0.0001 to 4 mm 2  or metal foam.  
     
     
         27 . The negative electrode for a nonaqueous secondary battery according to  claim 1 , wherein the current collector is formed of electrolytic metal foil.  
     
     
         28 . A process of producing the negative electrode for a nonaqueous secondary battery of  claim 4 , which comprises applying a slurry comprising the active material particles, the electro-conductive carbon material, a binder, and a diluting solvent to a surface of the current collector, drying the coating to form the active material layer, and electroplating the active material layer with the electro-conductive material having low capability of forming a lithium compound to form the surface coating layer.  
     
     
         29 . A process of producing the negative electrode for a nonaqueous secondary battery of  claim 4 , which comprises applying a slurry comprising the active material particles, the electro-conductive carbon material, a binder, and a diluting solvent to a surface of the current collector, drying the coating to form the active material layer, and depositing the electro-conductive material having low capability of forming a lithium compound on the active material layer by sputtering, chemical vapor deposition or physical vapor deposition to form the surface coating layer.  
     
     
         30 . A process of producing the negative electrode for a nonaqueous secondary battery of  claim 25 , which comprises forming a coat of a material different from the material making up the current collector on a carrier foil to a thickness of 0.001 to 1 μm, electroplating the carrier foil having the coat with the material making up the current collector to form the current collector, applying a slurry comprising the active material particles, the electro-conductive carbon material, a binder, and a diluting solvent to a surface of the current collector, drying the coating to form the active material layer, electroplating the active material layer with the electro-conductive material having low capability of forming a lithium compound to form the surface coating layer, and separating the current collector from the carrier foil.  
     
     
         31 . A nonaqueous secondary battery having the negative electrode for a nonaqueous secondary battery according to  claim 1.