Method for judging quality of lithium nickel composite oxide and positive electrode using lithium nickel comoposite oxide

Abstract

A positive electrode active material quality judgment method that can easily and accurately judge the quality of a positive electrode active material used in a non-aqueous electrolyte secondary cell without having to complete the positive electrode. The positive electrode active material quality judgment method includes: heating a positive electrode active material mainly made of a lithium nickel composite oxide to a temperature x (° C.) of 200° C. or higher and 1500° C. or lower; measuring the amount of carbon dioxide gas occurring from the heating; and the positive electrode active material as a suitable positive electrode active material when the positive electrode active material satisfies formulas 1 and 2: y <(0.27 x −51)/1000000(200≦ x <400)  formula 1 y <57/1000000(400≦ x ≦1500)  formula 2 where x is the heating temperature x (° C.) and y is the amount of carbon dioxide gas (mole/g) occurring per 1 g of the positive electrode active material in the heating to the heating temperature x (° C.).

1 . A quality judgment method for a positive electrode active material having a lithium nickel composite oxide, the method comprising the steps of:
 a heating step of heating the positive electrode active material to a temperature x (° C.) of 200° C. or higher and 1500° C. or lower in an inactive gas atmosphere;   a measuring step of measuring the amount of carbon dioxide gas generated from the heating; and   a judging step of judging the positive electrode active material as a suitable positive electrode active material when the positive electrode active material satisfies formulas 1 and 2:
     y <(0.27 x− 51)/1000000(200 ≦x< 400)  formula 1
 
     y< 57/1000000(400 ≦x≦ 1500)  formula 2
 
   where x is the heating temperature x (° C.) and y is the amount of carbon dioxide gas (mole/g) generated per 1 g of the positive electrode active material in the heating to the heating temperature x (° C.).   
     
     
         2 . The quality judgment method for a positive electrode active material having a lithium nickel composite oxide according to  claim 1 , wherein the heating temperature x (° C.) is 400° C. or higher and 500° C. or lower. 
     
     
         3 . The quality judgment method for a positive electrode active material having a lithium nickel composite oxide according to  claim 1 , wherein the measurement of the amount of carbon dioxide gas in the measuring step is carried out by gas chromatography. 
     
     
         4 . The quality judgment method for a positive electrode active material having a lithium nickel composite oxide according to  claim 1 , wherein the inactive gas atmosphere is an argon gas atmosphere. 
     
     
         5 . The quality judgment method for a positive electrode active material having a lithium nickel composite oxide according to  claim 1 , wherein the mass percentage of the lithium nickel composite oxide in the positive electrode active material is 50 mass % or more.