Electrode for electrochemical cell, method of manufacturing the same, and electrochemical cell includng the electrode

Abstract

An electrode for an electrochemical cell is provided. The electrode comprises an electrode active material coated on a current collector. The surface of the electrode active material has a greater porosity than the portion nearest the current collector. The electrode includes an active material with controlled porosity, where the porosity of the inner portion is equal to or less than the porosity of the surface of the electrode after the electrode is roll-pressed. As a result, the impregnating characteristics of the electrolytic solution are improved and decreases in capacity upon charging and discharging at high rates are prevented. Therefore, excellent charge and discharge characteristics are obtained. In addition, cells including the inventive electrodes exhibit excellent charge and discharge characteristics.

1 . An electrode for an electrochemical cell comprising an electrode active material coated on a current collector, wherein a porosity of the electrode active material near a surface of the electrode active material is greater than a porosity of the electrode active material near the current collector.  
   
   
       2 . The electrode of  claim 1 , wherein the surface of the electrode active material which contacts an electrolytic solution has the greatest porosity.  
   
   
       3 . The electrode of  claim 1 , wherein the electrode active material is manufactured by sintering an active material and a pore forming material.  
   
   
       4 . The electrode of  claim 3 , wherein the pore forming material is selected from the group consisting of thermally decomposable materials, materials capable of dissolving in an electrolytic solution and mixtures thereof.  
   
   
       5 . The electrode of  claim 4 , wherein the thermally decomposable material comprises a compound selected from the group consisting of ammonium carbonate, ammonium bicarbonate, ammonium oxalate and mixtures thereof.  
   
   
       6 . The electrode of  claim 4 , wherein the material capable of dissolving in the electrolytic solution comprises a compound selected from the group consisting of LiClO 4 , LiBF 4 , LiPF 6 , LiCF 3 SO 3 , and mixtures thereof.  
   
   
       7 . The electrode of  claim 3 , wherein the pore forming material is present in the electrode active material in an amount ranging from about 0.1 to about 10% by weight based on the total weight of the electrode active material.  
   
   
       8 . An electrochemical cell comprising the electrode of any of  claims 1  to  7 .  
   
   
       9 . The electrochemical cell of  claim 8 , wherein the electrochemical cell is selected from the group consisting of lithium ion batteries and lithium ion polymer batteries.  
   
   
       10 . A method of manufacturing an electrode for an electrochemical cell, the method comprising: 
 coating a current collector with an electrode active material;    coating the electrode active material with a mixture of a pore forming material and the electrode active material to form an electrode;    roll-pressing the electrode; and    sintering the roll-pressed electrode.    
   
   
       11 . A method of manufacturing an electrode for an electrochemical cell, the method comprising: 
 coating a current collector with an electrode active material;    coating the electrode active material with a pore forming material to form an electrode;    roll-pressing the electrode; and    sintering the roll-pressed electrode.    
   
   
       12 . The method of  claim 10 , wherein the pore forming material is selected from the group consisting of thermally decomposable materials, materials capable of dissolving in an electrolytic solution and mixtures thereof.  
   
   
       13 . The method of  claim 12 , wherein the thermally decomposable material comprises a compound selected from the group consisting of ammonium carbonate, ammonium bicarbonate, ammonium oxalate and mixtures thereof.  
   
   
       14 . The method of  claim 12 , wherein the material capable of dissolving in the electrolytic solution comprises a compound selected from the group consisting of LiClO 4 , LiBF 4 , LiPF 6 , LiCF 3 SO 3 , and mixtures thereof.  
   
   
       15 . The method of  claim 10 , wherein the pore forming material is present in the electrode in an amount ranging from about 0.1 to about 10% by weight based on the total amount of the electrode active material.  
   
   
       16 . The method of  claim 11 , wherein the pore forming material is selected from the group consisting of thermally decomposable materials, materials capable of dissolving in an electrolytic solution and mixtures thereof.  
   
   
       17 . The method of  claim 16 , wherein the thermally decomposable material comprises a compound selected from the group consisting of ammonium carbonate, ammonium bicarbonate, ammonium oxalate and mixtures thereof.  
   
   
       18 . The method of  claim 16 , wherein the material capable of dissolving in the electrolytic solution comprises a compound selected from the group consisting of LiClO 4 , LiBF 4 , LiPF 6 , LiCF 3 SO 3 , and mixtures thereof.  
   
   
       19 . The method of  claim 11 , wherein the pore forming material is present in the electrode in an amount ranging from about 0.1 to about 10% by weight based on the total weight of the electrode active material.