Positive electrode for lithium-ion secondary battery and lithium-ion secondary battery

Abstract

An object of the present invention is to provide a novel positive electrode which is produced using a rubber being an inexpensive material and is capable of enhancing a charge and discharge capacity and cyclability of a lithium-ion secondary battery, and the lithium-ion secondary battery composed of the positive electrode. In the lithium-ion secondary battery, the positive electrode comprises a current collector and an electrode layer formed on a surface of the current collector, the electrode layer comprises an active material, an electrically-conductive additive and a thermosetting resin binder subjected to thermosetting, and the active material comprises a sulfur-based positive-electrode active material prepared by heat-treating a starting material comprising a rubber and sulfur under a non-oxidizing atmosphere.

What is claimed is: 
     
         1 . A positive electrode for a lithium-ion secondary battery comprising a current collector and an electrode layer formed on a surface of the current collector,
 wherein the electrode layer comprises an active material, an electrically-conductive additive and a thermosetting resin binder subjected to thermosetting, and   the active material comprises a sulfur-based positive-electrode active material prepared by heat-treating a starting material comprising a rubber and sulfur under a non-oxidizing atmosphere.   
     
     
         2 . The positive electrode for a lithium-ion secondary battery of  claim 1 , wherein the thermosetting resin binder comprises at least one of a polyimide resin and a polyamide-imide resin. 
     
     
         3 . The positive electrode for a lithium-ion secondary battery of  claim 1 , wherein compounding ratios of the active material, the electrically-conductive additive and the thermosetting resin binder in the electrode layer are 30 to 95% by mass, 2 to 40% by mass and 3 to 30% by mass, respectively based on the total compounding amount of the three components. 
     
     
         4 . The positive electrode for a lithium-ion secondary battery of  claim 1 , wherein a heat-treating temperature when preparing the sulfur-based positive-electrode active material is from 250° C. to 550° C. 
     
     
         5 . The positive electrode for a lithium-ion secondary battery of  claim 1 , wherein the starting material of the sulfur-based positive-electrode active material further comprises a vulcanization accelerator. 
     
     
         6 . The positive electrode for a lithium-ion secondary battery of  claim 1 , wherein the starting material of the sulfur-based positive-electrode active material further comprises an electrically-conductive carbon material. 
     
     
         7 . The positive electrode for a lithium-ion secondary battery of  claim 6 , wherein the electrically-conductive carbon material is a carbon material having a graphite structure. 
     
     
         8 . The positive electrode for a lithium-ion secondary battery of  claim 6 , wherein the starting material of the sulfur-based positive-electrode active material comprises 250 to 1500 parts by mass of the sulfur, 3 to 250 parts by mass of the vulcanization accelerator and 5 to 50 parts by mass of the electrically-conductive carbon material based on 100 parts by mass of the rubber. 
     
     
         9 . The positive electrode for a lithium-ion secondary battery of  claim 1 , wherein a total content of the sulfur in the sulfur-based positive-electrode active material is not less than 50% by mass. 
     
     
         10 . A lithium-ion secondary battery comprising the positive electrode for a lithium-ion secondary battery of  claim 1 .