Positive-electrode active material for non-aqueous secondary battery and method for producing the same

Abstract

The present invention provides a positive-electrode active material for non-aqueous secondary battery comprising a sodium transition metal composite oxide represented by Formula: Na x Fe 1-y M y O 2 , wherein 0.4≦x≦0.7, 0.25≦y<1.0, and M is at least one element selected from the group consisting of manganese, cobalt and nickel, the sodium transition metal composite oxide having a crystal structure substantially composed of P6 3 /mmc alone.

What is claimed is: 
     
         1 . A positive-electrode active material for non-aqueous secondary battery comprising a sodium transition metal composite oxide represented by Formula:
   Na x Fe 1-y M y O 2 ,   wherein 0.4≦x≦0.7, 0.25≦y<1.0, and M is at least one element selected from the group consisting of manganese, cobalt and nickel, the sodium transition metal composite oxide having a crystal structure substantially composed of P6 3 /mmc alone.   
     
     
         2 . The positive-electrode active material according to  claim 1 , wherein the ratio of a peak intensity assigned to the (110) plane to a peak intensity assigned to the (016) plane is 0.30 to 2.00 according to powder X-ray diffractometry. 
     
     
         3 . The positive-electrode active material according to  claim 1 , wherein the integral width of a peak assigned to the (016) plane is 0.10° to 1.00° according to powder X-ray diffractometry. 
     
     
         4 . The positive-electrode active material according to  claim 1 , wherein the integral width of a peak assigned to the (110) plane is 0.10° to 0.30° according to powder X-ray diffractometry. 
     
     
         5 . The positive-electrode active material according to  claim 1 , wherein M is manganese. 
     
     
         6 . A method for producing a positive-electrode active material for non-aqueous secondary battery comprising a sodium transition metal composite oxide represented by Formula:
   Na x Fe 1-y M y O 2 ,   wherein 0.4≦x≦0.7, 0.25≦y<1.0, and M is at least one element selected from the group consisting of manganese, cobalt and nickel, the method comprising:   a precipitate formation step of obtaining a precipitate of a transition metal composite compound from a transition metal ion-containing aqueous solution,   a heat treatment step of heat treating the precipitate from the precipitate formation step to obtain a transition metal composite oxide precursor,   a mixing step of mixing the precursor from the heat treatment step with at least a sodium compound to obtain a raw material mixture, and   a calcination step of calcining the raw material mixture from the mixing step to obtain a calcined product.   
     
     
         7 . A method for producing a positive-electrode active material for non-aqueous secondary battery comprising a sodium transition metal composite oxide represented by Formula:
   Na x Fe 1-y M y O 2 ,   wherein 0.4≦x≦0.7, 0.25≦y<1.0, and M is at least one element selected from the group consisting of manganese, cobalt and nickel, the method comprising:   a precipitate formation step of obtaining a precipitate from a transition metal ion-containing aqueous solution, the precipitate containing a transition metal composite compound other than a hydroxide as a main component,   a mixing step of mixing the precipitate from the precipitate formation step with at least a sodium compound to obtain a raw material mixture, and   a calcination step of calcining the raw material mixture from the mixing step to obtain a calcined product.   
     
     
         8 . The method according to  claim 7 , wherein the main component of the precipitate is a transition metal composite carbonate salt. 
     
     
         9 . The method according to  claim 7 , wherein the method further comprises a heat treatment step of heat treating the precipitate from the precipitate formation step to obtain a transition metal composite oxide, and
 the mixing step is a step of mixing the transition metal composite oxide with at least a sodium compound to obtain a raw material mixture.   
     
     
         10 . The method according to  claim 6 , wherein the heat treatment temperature in the heat treatment step is 600° C. to 1000° C. 
     
     
         11 . The method according to  claim 9 , wherein the heat treatment temperature in the heat treatment step is 600° C. to 1000° C. 
     
     
         12 . The method according to  claim 6 , wherein the transition metal ion-containing aqueous solution in the precipitate formation step is an aqueous transition metal sulfate salt solution. 
     
     
         13 . The method according to  claim 7 , wherein the transition metal ion-containing aqueous solution in the precipitate formation step is an aqueous transition metal sulfate salt solution. 
     
     
         14 . A composition for a positive-electrode for non-aqueous secondary battery comprising the positive-electrode active material according to  claim 1  and a binder. 
     
     
         15 . A positive-electrode for non-aqueous secondary battery comprising a positive-electrode collector and a positive-electrode active material layer formed on the positive-electrode collector, wherein the positive-electrode active material layer comprising the positive-electrode active material according to  claim 1 . 
     
     
         16 . A non-aqueous secondary battery comprising a positive-electrode according to  claim 15 , a negative-electrode and non-aqueous electrolytic solution.